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By Demaerel. J. P.

Arsenic plays a major role during electroreflning of copper. Both the arsenic content in the anode and the arsenic concentration of the electrolyte have, in conjunction with other impurities such as lead, antimony, bismuth and oxygen, a direct influence on the quality of the cathode. The mechanisms are currently slime. inclusion and precipitation of insoluble compounds in the bulk of the electrolyte. Arsenic has also been reported to have a depassivating effect on the anode. An influence on the anode slime adhesion has also been found. A literature survey is given and these data are compared with and completed by our own results based on lab and pilot scale experiments as well as on Olen tank.house practice.

Jan 1, 1987

By Yuanbo Zhang, Zhixiong You, Zijian Su, Bingbing Liu, Guanghui Li, Guang Yang, Tao Jiang

Sodium stannate is widely used in the electroplating and tin alloy industry. But the traditional processes for sodium stannate production are characterized by long flowsheet, high production cost and strict requirement for the equipments, etc. In this study, a novel process for sodium stannate preparation from cassiterite concentrate and sodium carbonate via roasting in CO/CO2 mixed gas then followed by leaching was developed. The effects of roasting parameters on the Sn leaching efficiency were conducted. A Sn leaching efficiency of 77.2% was obtained under the optimal conditions. Sodium stannate (Na2SnO3·3H2O) with a purity of 95.8% was produced by the new process, which is better than that specified for the industrial first-grade product.

Jan 1, 2014

By Nickolas J. Themelis

Nearly thirty two million tons of municipal solid wastes (MSW) are combusted annually in over one hundred U.S. Waste-to-Energy (WTE) power plants, thus reducing the use of fuel oil by about 1.6 billion gallons of fuel oil One of the advanced WTE processes is the 0.9-million ton/y SEMASS facility at Rochester, Mass. Most of the combustion in the three giant combustion chambers occurs while the injected shredded wastes are in suspension, i.e., in flash combustion mode. The velocity, temperature, and concentration profiles in the SEMASS combustion chamber were simulated by representing the combustible fraction of MSW by the simplified formula C6HIO04 and using the CFD program Fluent to solve the turbulent energy and mass transport equations. After validation against plant data, this model will be used to examine options for increasing the productivity of WTE combustion chambers, such as optimum distribution of primary and secondary air and oxygen enrichment.

Jan 1, 2003

By D. G. Mason

During the design of copper refinery tankhouses, there is a need to develop mass balance calculations for many process components, so that optimum physical plant configuration is achieved. Each mass balance is complex, possibly with over 120 interactive variables as basic input data. Recent developments in tankhouse design (e.g. permanent cathodes) have greatly increased the design options available for any project, multiplying even further the requirement for calculations. In the past these calculations were tedious and susceptible to human error. A comprehensive computer program can now simplify the task of the process metallurgist, enabling more sophisticated and sensitive plant designs to be produced. The paper describes the successful development of a flexible mass balance program that originallly was used in a feasibility study which had to be completed within a short time schedule. The program has been further developed and used for design and energy calculations; it can be usefully applied to existing plants to assess the impact of variations in operating parameters. The software takes account of staged liberation, electrolyte purification bleed and generates a reliable process inventory listing: it can also cope with stripper starting sheet options and disparate commercial circuits.

Jan 1, 1987

By Xuemei Zheng, Aiyuan Ma, Jing Li, Jinhui Peng, Shaohua Yin, Libo Zhang

Zinc recovery from zinc oxide flue dust (ZOFD) by ultrasound enhanced neutral leaching process was investigated. In this study, the effects of leaching temperature, liquid/solid ratio, leaching time and ultrasound power were studied, and the conventional leaching experiments were also performed. The experimental results showed that the leaching time was greatly shortened and the leaching rate of zinc was effectively improved by the assistance of ultrasound. The optimum conditions of ultrasound-assisted leaching were determined as leaching time 20 min, temperature 35℃, and the liquid/solid ratio of 5. Under these conditions, the leaching rate of zinc was close to 80% as the ultrasound power of 540W, which was increased by 7% or so, in comparison with that of conventional leaching process.

Jan 1, 2015

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 P. H. Chang, J. E. Gould

"Solidification structures and austenite decomposition in some spot welded O.05%C - O.3%Mn steels have been studied with the aid of a numerical thermal model. The model is a one dimensional finite difference formulation, and accounts for melting, temperature dependent thermal properties, effective heat transfer in the liquid, and contact resistances. The model was used to predict solidification conditions during resolidification of the nugget. These solidification conditions were correlated with the primary dendrite spacing using available primary dendrite spacings modelling. The model was also used to predict cooling rates in the temperature regime for austenite decomposition. These cooling rates were used to interpret the underlying microstructure.INTRODUCTIONThe metallurgical transformations which occur during the spot welding of low carbon steels have traditionally been characterized only in the most general of fashions. This is most probably due to the similarity of spot welded microstructures to other welded microstructures, and that the mechanical integrity of spot welds has not been a concern. In addition, little information about the particular thermal cycles experienced during spot welding has been available. The introduction of HSLA (microalloyed) sheet steels has, however, raised new concerns about the integrity of spot welds. These steels have on occasion shown irregular weldability, as well as brittleness in the weld nugget on destructive testing l - 4 .In response to these concerns, considerable work has been done attempting to characterize thermal cycles in spot welds 5-12. This has largely taken the form of thermal modelling, with the end purpose generally to estimate the size of the nugget formed. This work uses the thermal model developed at Inland Steel 13 ,14 to try and understand, in a more fundamental way, microstructural evolution in spot welds. Two facets of this microstructural evolution are examined in detail:"

Jan 1, 1986

By Guy Deschênes

In spite of the wide use of lead compounds to enhance cyanidation of free milling sulphide-bearing gold ores, an industrial control method was only implemented four years ago. This study presents the results of the investigation that led to the development of the on-line control technology. Two free milling sulphide-bearing gold ores and high purity minerals were used to develop and test the concept. The first ore contains 2.8 g/t Au, 6.2% pyrrhotite, 2.1% pyrite 0.6 % arsenopyrite, 0.1% chalcopyrite and 0.1% organic carbon. The second ore contains 10.4 g/t Au, 3.2% pyrite, 0.8% pyrrhotite and 0.38% chalcopyrite. The first ore showed a much higher oxidation rate in the pre-leach than the second one and consumed seven times more cyanide. A relation between the formation of thiosulphate and thiocyanate and the additions of lead nitrate were quantified. The ?reducing power?, a titration with permanganate, predominantly determines the concentration of thiosulphate and thiocyanate in cyanide solution. The relation between the reducing power and the addition of lead nitrate at various concentrations of pyrrhotite and chalcopyrite in the ores was established, providing a monitor/control strategy for lead nitrate addition.

Jan 1, 2006

By Brent W. Madsen

The acid-ferric sulfate leaching of low-grade sulfide copper mine waste provides more than 10 percent of the U.S. supply of new copper, but recoveries and leaching rates are very low. In Federal Bureau of Mines research to improve the leaching process, experiments on 5- to 10-ton lots of mine-run ore were more revealing than bench-scale tests on fine ore. This report discusses the results obtained by leaching run-of-mine and minus 6-inch plus 112-inch samples of low-grade chalcocite-bearing mine waste. The samples were leached for 461 days and 61.6 and 37.7 percent of the copper was extracted from the minus 6-inch plus -112-inch and run-of- mine samples, respectively. A mixed kinetics model was applied successfully to the leaching of the sample with the fines removed where bulk solution transport was not rate controlling. The model, when applied to the run-of- mine ore, gave somewhat higher predicted copper extractions than experimentally determined. Subsequently, oxygen was introduced into the run-of- mine ore, leaching continued for an additional 312 days, and an additional 53.0 percent of the copper was extracted. Before the leaching experiment was dismantled and the residue sampled, the ore was treated with sulfur dioxide and its permeability was improved markedly. The results of each of these procedures are interpreted in relation to the attendant condition of the test.

Jan 1, 1976

By Marcio B. Fonseca

Nickel-cobalt laterite deposits have become the focus of attention for hydrometallurgical processing. Following the lessons of the second generation high pressure acid leach (HPAL) projects in Western Australia other Ni-Co laterite projects are now evaluating potential HPAL projects with a rigorous integrated approach that begins with geological modeling, resource estimation and metallurgical studies. The Vermelho nickel-cobalt laterite deposit has been under exploration and study for several years with investigations of various metallurgical processes. Recent HPAL studies have indicated that the nickel and cobalt laterite at this deposit is amenable to upgrading by silica rejection followed by pressure leaching. These studies have required a detailed geological investigation to generate a new resource model. The recent development of a sophisticated geological model integrated with a multi-element resource estimation for this complex tropical nickel laterite deposit in northern Brazil provides an example of the contribution of geology at the critical project stage where process technology decisions are made on relatively small samples of the total resource.\ Keywords: Ni Laterite, Geological Modeling, Resource Estimation

Jan 1, 2004

By Philip E. J. Green

Two of the cornerstones of total quality management, the use of statistical and problem solving tools, and the involvement of employees, are directly applicable to environmental protection. The reduction in variation decreases the chances of violations and mishaps. Involving employees in minimizing environmental impacts is critical. One mistake, even with the best technology, and your plant can be shut down, customers lost and fines and penalties imposed - your reputation and the environment damaged. Proven strategies for involving employees in environmental protection, and over-coming the frequently strong differences of opinions about what constitutes environmental protection, will be discussed.

Jan 1, 1992

By Heikki K. Jalkanen

Thermodynamic properties of copper-iron mattes and slag-matte distribution of copper and some minor matte constituents (Ni, Co, Mo, As, Sb and Bi) are discussed on? the basis of equilibrium measurements: a change from. oxidic to sulfidic solubility as the predominant form of dissolution of copper takes place as matte grade decreases. Distribution coefficients of minor matte constituents are complex functions of sulfur and/or oxygen potentials?. The distribution behaviour of different? metals can be qualitatively derived from their affinities to copper and stabilities. of their sulfides and oxides. The equilibrium results are compared with commercially observed values. from Outokumpu.Oy flash smelting furnace.

Jan 1, 1983

Smelter operating and environmental requirements demand high on-stream time (high reliability) from the primary smelter sulfur retention device - the sulfuric acid plant. The key to reliable smelter sulfuric acid plant operation is the gas cooling and cleaning system. Problems in the gas cleaning system cause corrosion, plugging, equipment failure, etc - plant down time, in the contact section of the plant. The last fifteen years have seen major changes in gas cleaning system design to the current standard of brick lined venturi scrubber, packed gas cooling tower with plate type liquor coolers and lead or plastic tube precipitators. The current-design offers improved impurity scrubbing along with increased reliability. In addition, a number of alternate gas cleaning systems have been offered. Chematics LAB System: Monsanto DuPont Dynawave System; Lurgi venturi scrubber with lead star gas cooler. This paper will review the design and operating advantages, disadvantages, and risk of the standard gas cleaning system and compare it to the alternate systems.

Jan 1, 1992

By M. Okido, H. Yamamoto, T. Sakamoto, R. Ichino, K. Kuroda

"Hydrogen absorption alloy films have been produced by molten salt electrolysis. Lanthanum-Nickel alloy film can be formed on a nickel substrate in KCl-NaCl-LaCb molten salts by electrolysis diffusion process. LaNi5 alloy was formed by mutual diffusion between La ·and Ni after La deposition on Ni substrate. Though several kinds of La-Ni compound existed in deposits, the alloy compounds on Ni substrate changed by electrolysis condition. According to the open-circuit potential measurement in molten salts after La electrodeposition, the formed compounds had a relation to the potential. In the case of the substrate electroplated a cobalt thin film on nickel, LaNi4_5Co0.5 was formed by the electrolysis in the molten salts with lanthanum ions. This ternary alloy film showed better hydrogen absorption behavior in cyclic charge/discharge test in alkaline solution.IntroductionHydrogen storage alloys have attracted attention as the active materials for batteries with the charge/discharge property at ambient temperature. The alloy of nickel and misch metal, mainly consisting of La and Ce, has been commercially 'used as a metal hydride with rechargeable property. In recent years, researches have been developed many kind of new alloys with better hydrogen absorption properties. The hydrogen absorbing alloy ingots are commonly produced by melting method of both metals in furnace, otherwise, prepared by mechanical grinding and metallurgical sintering technique with metal powders. The film is also made by vapor-phase techniques such as sputtering method, ion plating method, etc. ·We have proposed a new method to produce hydrogen absorbing alloy films by molten salts electrolysis technique [1-3]. The hydrogen absorbing film, LaNi5, Mg2Ni and CaNi5, were obtained in this process through controlling the electrolytic condition. The active metals, La, Mg and Ca, are electrodeposited on Ni substrate, diffuse into the substrate and form various kinds of intermetallic compounds. This technique provides a direct process using metal chlorides as resources to produce functional films without using active metals such as La, Ca and Mg."

Jan 1, 2000

By Pragna Bhakta

Newmont has investigated potential treatment options for low-grade refractory gold ores since 1988. After extensive R&D at Newmont?s laboratories, biooxidation pretreatment followed by ammonium thiosulfate leaching was selected for application to sulfidic preg robbing ores. A heap biooxidation and ammonium thiosulfate leaching demonstration facility was constructed in 1995 to conduct large-scale pilot tests at Newmont?s Carlin Operations. This paper presents Newmont?s experience with the recovery of gold from preg robbing ores using ammonium thiosulfate.

Jan 1, 2003

By Bo Yan, Jiaquan Zhang, Haibo Sun

"Based on the validation of steady-state isothermal mathematical model by a 0.4-scale water model for the single-strand slab casting tundish, the effect of varying pouring temperature on the flow, temperature field, and residence time distribution(RTD) of the liquid steel was studied by a transient hydrodynamic model. Due to the decreasing temperature of ladle stream over a casting period of 50 min, the direction of vortex flow at the downstream side of dam changes to clockwise from the anticlockwise at 4 min after the new teeming, and reverts to anticlockwise direction again at 43 min. Meanwhile, the melt flow state in the dam hole is also varying with time. For conventional isothermal water modeling, the RTD parameters obtained are much different as compared with the non-isothermal ones. For the flow control devices(FCD) design, however, the identical optimal scheme can be concluded from the point of view of isothermal modeling.IntroductionOriginally, tundish was adopted as a buffer and distributor to hold and allocate molten steel for sequence casting upon ladle exchange and to provide a desired steel flow rate to the mould below. With the increasing demand to strand quality, the tundish has become a critical metallurgical reactor to enhance inclusions removal, avoid reoxidation of molten steel, and prevent slag entrapment. The general trends to obtain these metallurgical effects are to optimize steel flow pattern and to extend the residence time of molten steel in the tundish through increasing the volume of tundish and/or using FCDs in the interior of the tundish."

Jan 1, 2012

By Hande Cavus, Ibrahim Yusufoglu, Cem Kahruman

"In this study, ammonium tetramolybdate (ATM) was obtained as the intermediate product of ammonium heptamolybdate tetrahydrate (AHM). The thermal decomposition mechanism of ATM was investigated under nonisothermal and isothermal conditions in air and inert gas atmospheres. Nonisothermal experiments were carried out by TGA/DTA/MS while TG was used for isothermal conditions. Characterization of the decomposition products were carried out by XRD and FT-IR. The thermal decomposition of ATM in air proceeds in a single step and forms M0O3 while [(ÍÇ4)2è]ïïï83Ìïè3 and molybdenum suboxide (Ìïè3.÷, ÷=0.025) were obtained in the first and the second steps of thermal decomposition in He, respectively. Activation energies, frequency factors and kinetic model equations were determined for thermal decomposition reactions. Fractional conversion-time diagrams were compared with diagrams drawn according to kinetic model equation.IntroductionM0O3 is usually used as catalyst in industry [1]. AHM is the basic source to produce molybdenum containing catalysts used in petrochemistry [2]. The oxides of Li, V, W, Te, Bi and Sn are doped in M0O3 to produce catalysts, which find commercial applications in the industry. The properties of M0O3 are affected by dissolution, settling, calcination, drying and thermal decomposition processes [1]. There are several studies in the literature about the thermal decomposition of AHM and the characterization of the decomposition products in different gas atmospheres and at various heating rates [3-19]."

Jan 1, 2012

By Chen Ya

Layered LiMn0.5Ni0.3Co0.2O2 was prepared from Mn(NO3)2, Ni(NO3)2, Co(NO3)2 and LiOH by co-precipitation and solid state reaction. XRD, C-V and galvanostatic charge-discharge methods were used to examine the structural and electrochemical characteristics. The LiMn0.5Ni0.3Co0.2O2 delivered a high discharge capacity of 167 mAh/g between 2.5 and 4.3 V with excellent cycling stability.

Jan 1, 2006

By Marc Verhaege

The effluent under investigation results from a catalic oxidation unit in which paraxylene is oxydised to terephtalic acid. The solution contains cobalt and manganese as their acetates in a concentration range of 0,4 - 1,2 g/I of cobalt and 0,8 - 2,4 g/l of manganese. Before being fed into the main waste stream treatment unit of the plant it is advisable to apply a petreatment step in which both metals are eliminated to a great extent from this effluent. Conventional treatment is done by precipitation of both metals either through pH increment with a base or by adding a suitable reagent producing insoluble species. The aim of this study was to look for a treatment (elimination of both metal species) in which no sludge or precipitate is formed.

Jan 1, 1995

By Jong-Jip Kim, J. G. Byrne, W. Kim, In-Ok Shim, John E. Flinn

"Two rapid solidification processes for 304 stainless steel were studied: centrifugal atomization (CA) in a helium atmosphere and atomization by exposing argon-containing melt to vacuum (VGA). Positron annihilation and x-ray line broadening measurements of explosively consolidated monoliths were used to clarify microhardness measurements as a function of annealing temperature. Interesting differences in positron response between CA and VGA materials are ascribed to more carbide formation in the CA material than in the VGA material in the 600 0C range. In addition, hot isostatic pressing of the CA material was examined as to the relations between mechanical behavior, pore shape, and relative density. A variable stress concentration factor is introduced into the theory to allow for changing pore shape as relative density increases.IntroductionThere are many potential advantages of rapid solidification processing (RSP), such as a high degree of matrix supersaturation, finely dispersed microstructures, improved chemical homogeneity, and retention of metastable phases, which have been studied extensively. To consolidate rapidly solidified material which is in powder form into useful shapes often requires subjecting the material to elevated temperature for extended periods of time under mechanical forces, as in hot isostatic pressing or hot extrusion. In such cases, some of the characteristics of the rapid-cooling step can be strongly affected. An alternative is dynamic consolidation (1), for example by explosive forming, where the time frame at least is extremely short.In the present work, effects of the consolidation processes of hot isostatic pressing (HIP) and explosive forming in a die are examined. The particular material is 304 stainless steel. The characteristics of both RS and VGA 304 stainless-steel powders were described by Wright, Flinn, and Korth (2) earlier."

Jan 1, 1988