Search Documents

By B. Fresz

Before aluminum is utilized in automotive bodies, the longevity of the electrodes employed in the resistance spot welding of aluminum must increase. This paper explores the affects of electrode composition on electrode life. To compare these variables, electrode tests were completed on a Taylor Wield welding machine using, Cu-Cr, Cu- Zr, Cu-Cr-Zr, Cu-Be, and Glidcop electrodes tested to 12.5%, 25%, 50%, 100%, and 150% lifetimes. Electrode diameters were found via a magnification technique using a PULNIM video camera attached to a low magnification Wild Heerbrugg stereo-zoom microscope. From these measurements, graphs of electrode life verses face diameter and weld number verses face diameter were created. Analyses of these graphs suggest that a single failure mechanism is responsible for electrode failure, though the number of welds until failure (100% electrode life) varied with composition (700-2000 welds).

Jan 1, 1999

By Takeshi Yoshikawa

For the sake of effective control of titanium-compound inclusions in the steel-making processes, especially for stainless steel production, the influences of alloying elements of chromium, nickel, manganese, molybdenum, copper and oxygen on the thermodynamic property of titanium in molten iron were investigated at 1873K. At a certain titanium potential controlled by the coexistence of Ti3O5 and Ti2O3 doubly saturation of steels, the interaction parameters between alloying elements and titanium in molten iron were determined as follows. [ ] From the investigations on the equilibrium of titanium deoxidation in molten iron, the activity coefficient of titanium and the first order interaction parameter between oxygen and titanium were determined as follows. [ ] Also, deoxidation equilibrium for titanium in molten 304 stainless steel was measured and compared with the calculated results using the determined interaction parameters.

Jan 1, 2006

By M. A. Gimenes

The utilization of chlorination in extractive metallurgy and advanced ceramics areas has been widely investigated as a preparative route in order to obtain intermetallic compounds, which are used as precursors in the development of new materials and process. The major processes of decomposition of rare-earth ores use sulfuric acid and sodium hydroxide at high temperatures, however there is not much work concerning chlorination. In this work, a systematic study of the reaction between xenotime (REPO4), chlorine and carbon has been performed. Particular emphasis was on kinetic studies to establish optimized conditions for the reaction. The kinetics of chlorination of xenotime raw material by rare-earth elements/compounds has been studied over a temperature range from 600°C to 950°C. The influence on the rate of conversion of xenotime to RECl3 on temperature, partial pressure of chlorine, carbon content, and particle size were investigated. A global rate equation that includes these parameters has been developed. The results show that the process follows the unreacted core-shrinking model with a formation of a porous product layer. The powder X ray-diffraction technique corroborated this model showing clearly the patterns related to the formation of yttrium oxychloride (YOCl), indicating that the reaction mechanism involves the presence ofan intermediate step before the formation of lanthanide chloride.

Jan 1, 2000

By M. M. Monte

A method for removing metallic mercury from contaminated tailing, using the flotation process, is described. In order to define some relevant parameters for the mercury flotation system, microflotation and electrophoretic mobility tests were carried out on (pure) metallic mercury in the presence of several surfactants. Based on the results obtained from fundamental studies a series of bench scale flotation experiments with mercury containing tailings from two wetland sites in Brasil were done. The results of microflotation tests with mercury showed that by using cetyl trimethyl ammonium bromide, an increase in mercury flotability is observed in the acid pH range, whereas in the presence of potassium oleate the highest mercury flotability was found in the alkaline pH region. The mercury flotability using potassium amyl xanthate was improved by the addition at sodium dithionate as an activator. The bench scale flotation tests with contaminated tailings from Poconé (brazilian wetland site) showed a recovery of 70% when sodium dithionate was used as activator and potassium amyl xanthate as collector. The resulting coefficient of separation is around 60%. However, the results of the flotation experiments with fine fractions from amalgamation tailings from Peixoto de Azevedo (brazilian wetland site) showed a low mercury recovery (32%).The results from this work suggest that since in the Poconé site tailings, the metallic mercury is not completely associated to the finer particles, the flotation process to recover the metallic mercury seems very promisor.

Jan 1, 1996

By Norihiro Murayama

Syntheses of zeolitic materials were carried out from coal fly ash by alkali hydrothermal treatment as part of the reuse and recycle technologies of coal ash, For the obtained zeolites, the cation exchange capacity and acid resistance, which are very important in the practical use of cation exchanger in aqueous solution, are investigated during this stufY, The cation exchange amounts of the NaP, CaP and K-CHA zeolites are measured for various cations such as K+, Na +, NH4+ Ca2+, Mg2+, Pb2+, Cd2+ and so on. The change in crystallization degree are researched as a function of pH. The simultaneous removal ability of NH4+ and PO43- in solution is examined for an example of the water purification with CaP zeolite. From these results, the characteristic and its mechanism of cation exchange are clarified for the various zeolitic materials obtained from coal fly ash.

Jan 1, 2003

By Benjamin P. Hay

Complexation of a metal ion to a ligand often results in structural changes that introduce steric strain within the ligand. A design criterior:1 for ligands that will complex metal ions more strongly is to choose Iigar:1d architecture, that minimizes this strain. This paper describes how molecular mechanics models can be used to define the degree of ligand binding site organization in terms of' ,strain energies associated with conformational reorganization and distortion of the binding conformer. This approach yields a method to predict how modifications to ligand structure will affect metal binding affinity.

Jan 1, 1999

A novel pressure leaching process for platinum group metal (PGM) feedstocks is described. The process is particularly well suited for treatment of ores or concentrates that are too low grade for economic processing by the conventional smelting/leaching process. Operating conditions have been identified under which gold, the PGM's and the base metals dissolve simultaneously in a pressure leaching autoclave. The product of this leaching process can then be treated by one of several flowsheets, of which the preferred will likely involve solid/liquid separation, followed by precipitation (or adsorption on activated carbon) of gold and the PGM's, followed by copper solvent extraction/electrowinning. Depending on the concentrations of nickel and cobalt, the copper raffinate would either be partially recycled to the autoclave to allow NilCo concentrations to build up, or it would proceed directly to a Ni/Co refinery. This paper deals with the pressure leaching process and the recovery of gold and the PGM's from the pressure leach product.

Jan 1, 2000

By Gang Qi

The solubility of nitrogen in pure molybdenum was measured over the temperature range 2173 to 2473 K and up to one atmosphere (101 kPa) of nitrogen gas pressure. Both thermochemical and kinetic aspects of this phenomenon were considered in this study. The solution of nitrogen in molybdenum may be expressed by the reaction 1/2N2(g) = {N} (Mo,s), for which the standard Gibbs energy is given by the expression {A}G° = 78,500 + 27.36T Joules/g atom N. The formation of molybdenum nitrides, specifically Mo2N, was considered. Attention was also focused on the mechanism of nitrogen solution in molybdenum. Estimates of the diffusivity of nitrogen atoms in solid molybdenum were derived from the kinetic data.

Jan 1, 1991

By M. Wenzel, Dang Thanh Tung, Nguyen Anh Duc, Nguyen Huu Luong, Dang Van Sy, N. Kelly, K. Gloe, K. Kretschmer, Phuc Nguyen Le, K. Schnaars, S. Robles M, L. Götzke, J. J. Weigand

The recovery of rare earth metals from secondary sources has attracted much attention due to their ever expanding demand in the high-tech industry. The studies reported here focus on the hydrometallurgical recovery of lanthanum and cerium from spent fluid catalytic cracking (FCC) catalysts in a two-step process: leaching with nitric acid and solvent extraction by tri-n-butyl phosphate (TBP) and di(2-ethylhexyl)phosphoric acid (D2EHPA). The experiments show a high dissolution yield of about 93% lanthanum and 42% cerium in a single leaching step with 2 M (126 g/L) HNO3 at 80 °C; only 11% aluminum has been dissolved simultaneously. In the subsequent solvent extraction step the best results for this leach liquor could be achieved using a 1:1 mixture of 25% (v/v) TBP (0.92 M) and 25% (v/v) D2EHPA (0.76 M) in n-decane without the need for any pH adjustment. In that case La(III) and Ce(III) can be extracted with 60% and 74% yield respectively in one stage from the majority of accompanying matrix elements. In particular no extraction of Al(III) could be observed under these conditions.

Jan 1, 2016

By Do-Hyeong Kim, Tae-Jung Kim, Seung-Yeon Won, Jong-Jin Pak, Min-Kyu Paek

Liquid iron alloys containing V, Mo, and Ni can be produced by the carbothermic reduction of spent catalysts used in petrochemical industry. Thermodynamics of carbon in these alloy melts is important for refining these alloys. In the present study, the carbon solubility in Fe-V, Fe-Mo, Fe-Ni, Fe-V-Mo, Fe-V-Ni, Fe-Mo-Ni and Fe-V-Mo-Ni alloy melts of various compositions was measured at 1873 K. The temperature dependency of vanadium effect on carbon solubility in liquid iron was also measured in the temperature range from 1823K to 1923K. The additions of vanadium and molybdenum significantly increased the carbon solubility in liquid iron alloys while nickel decreased the solubility. The experimental results were thermodynamically analyzed using Lupis’ relation at constant activity to determine the first- and the second-order interaction parameters of vanadium, nickel and molybdenum on carbon at carbon saturated condition. Using thermodynamic parameters determined in the present study, the carbon solubility in Fe-V-Mo-Ni alloy melts of various composition were accurately predicted and verified experimentally at 1873 K.

Jan 1, 2014

By D. M. Jones

Dust generation data have been obtained from 19 industrial Outokumpu flash furnaces. Statistical analyses of the data have been carried out and the most significant factors affecting dust generation evaluated. The results indicate that dust production may most effectively be minimized by: 1) Minimizing the distance between the molten slag and the furnace roof 2) Optimizing burner design and combustion parameters.

Jan 1, 1996

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

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 Bhagyadhar Bhoi, Chitta Ranjan Mishra, Hara Prasanna Mishra

"In the Sukinda Valley of Orissa, India, the total quantity of nickel ore reserves comprising of both lateritic and chromite over burden(COB) have been estimated at around 231 million tonnes containing 0.3 to 0.9% Ni. While mining of one tonne of Chromite ore, around 6-7 tonnes of chromite over burden are removed. These overburden materials are disposed as waste materials, which causes lot of environmental hazards and ecological imbalance. India imports a large amount of nickel and ferro-nickel to meet its growing demands in various sectors. For import substitutions, efforts have been made to produced ferro-nickel from the lean deposits of nickel bearing lateritic ores/ chromite over burden materials by reduction roasting followed by magnetic separation and then the nickel rich magnetic fraction is smelted to produce ferro-nickel. It has been possible to produce ferro-nickel of grade varying from 4-25% nickel.IntroductionDuring mining of chromite ore, large quantities of overburden materials are being generated. The materials amount to approximately 10 million tones per year contain around 0.3-0.9% Ni, 0.02-0.06% Co, 20-50% Fe and 4-9% Cr2O3 depending upon the location and the depth of the mine. These materials presently do not find any application for the extraction of nickel due to lack of a suitable technology. The materials are also unsuitable for ferro-nickel making because of their very high iron to nickel ratio. The country is seriously looking for a suitable technology to utilize these resources as its entire domestic requirements of nickel is met though imports. In this connection, a systematic approach has been made at the Institute of Minerals and Materials Technology, Bhubaneswar to develop a process for ferro-nickel making from this indigenous resource."

Jan 1, 2011

By N. D. Schupp

The Doe Run Company's Herculaneum, Missouri lead smelter has existed in continuous operation since 1892. Throughout the history of the plant extensive developments have been made to improve throughput, increase productivity, decrease operational costs and improve technology, while remaining an environmentally responsible producer of high quality primary lead in the international market. This paper provides an overview of the Herculaneum smelter, focusing on the most recent configuration of the operations. The paper includes discussion on all the aspects of primary lead production at the Herculaneum smelter.

Jan 1, 2000

By M. K. Mohan

During the processing of metals like Cu, Ni, Co, large quantities of solutions, which contain co- products such as Sb, Cd, Pb etc. are generated. These solutions if processed to recover the metals help in conservation of metals as well as environment preservation. The present study was taken up to recover antimony from process solutions using zeolites. The effect of pH of the solution, time and type of zeolite viz., chabazite, mordenite, erionite and clinoptilolite on the sorption of antimony was investigated. Rate of sorption increases with pH and about 77-pct. antimony sorption was observed with chabazite at a pH of 6. Optimal conditions were established for the maximum recovery of antimony fiom process solutions. The mechanism of sorption for Sb was proposed in terms of adsorption and intraparticle diffusion. The calculated adsorption constants from Langmuir and Freundlich equations indicated that the adsorption of antimony on chabazite was strong.

Jan 1, 1999

By W. R. McDonald

The U.S. Bureau of Mines investigated treatment of gold and silver refractory ores and concentrates that respond poorly to conventional cyanidation techniques due to the complex mineralogy of the ore. Three types of ores were investigated: gold locked placer sands, gold locked in sulfides, and gold that is robbed from the pregnant cyanide solutions by minerals in the ore. Ore treatment included grinding, flotation, cyanidation, air oxidation, pressure oxidation, hypochlorite oxidation, roasting, and carbon in leach.

Jan 1, 1991

By H. Soto, J. Jara, F. Nava

A method has been developed to recover cyanide and copper from solutions containing copper complexes and thiocyanate. Copper is precipitated as copper thiocyanate or as copper cyanide depending on pH and the concentrations of thiocyanate and cyanide in the effluent. The copper precipitate assays over 50% copper and presents good dewatering characteristics. After settling it can be separated from the effluent by filtration. The solution containing the bulk of the cyanide is then oxidized with ozone to transform the remaining thiocyanate into cyanide. This results in a regenerated solution rich in free cyanide that can be recycled to the cyanidation process. Careful control of the pH of the solution is required. First, pH of the effluent is lowered to optimize the precipitation and oxidation stages, then the pH is restored to an alkaline value to regenerate the cyanide solution. Recoveries of over 96% copper and cyanide were obtained in laboratory tests using industrial solutions. With this procedure, cyanocidic gold/copper ores could be treated economically by heap leaching, since the cyanide consumed by the copper impurities could be regenerated at very low cost (most of the cost of cyanide regeneration would be compensated by the copper credits). In order to achieve this, a bleed of the barren solution could be treated by the proposed method, and then recycled to the leaching step. The volume of solution to be treated should be large enough to keep a cyanide/copper molar ratio higher than 3:1. This would assure that copper does not cause undue interferences in the leaching or the carbon adsorption stages. If the thiocyanate content is low, the oxidation stage can be avoided, and the solution can be recycled to the leaching stage directly after the solid-liquid separation stage.

Jan 1, 1997

By K. L. Money, R. R. Bleakney, R. H. Hanewald

The processing of EAF baghouse dusts, rolling mill scales, and belt grinding swarfs from the specialty steel industry will be reviewed. In addition, the INMETCO process has been modified so as to recover nickel, chromium and iron from many other waste materials such as pickling solutions, filter cakes, spent nickel and chromium plating baths, super alloy wastes, and nickel-cadmium batteries. INMETCO is the only North American company presently capable of recycling nickel-cadmium batteries by high temperature metals recovery.

Jan 1, 2000

By Guo Chen, Xuefeng Liao, Tu Hu, Shengzhou Zhang, Hongying Xia, Jinhui Peng, Libo Zhang

Pine nut shell is as raw material for preparation of high surface area activated carbon (HSAAC) by microwave induced KOH activation. The effects of microwave power, activation duration and KOH/C mass rate (R) on the iodine adsorption capability and activated carbon yield were investigated. Additionally the surface characteristics of HSAAC were characterized by nitrogen adsorption isotherms and SEM. The operating variables were optimized utilizing the response surface methodology and were identified microwave power 738W, activation duration 17 min, and R 4, corresponding to a yield of 46.28 % and an iodine number of 2154 mg/g. The key pore structure parameters of HSAAC such as the Brunauer–Emmett–Teller (BET) surface area and total pore volume were estimated to be 3819 m2/g and 2.09 mL/g, respectively. The findings strongly support the feasibility of microwave heating for preparation of HSAAC from spent pine nut shell by microwave induced KOH activation.

Jan 1, 2016