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By Alan J. Hurd

"New insights into the development of microstructure in sol-gel films have recently been revealed by several diagnostic techniques, including imaging ellipsometry, ""chemical imaging"" by fluorescent tracers, light scattering from capillary waves, and finite-element modeling. The evolution of porosity during the continuous transition from dilute sol to porous solid in restricted geometries such as films and fibers is becoming clearer through fundamental understanding of evaporation dynamics and capillarity.IntroductionWith sol-gel processing, the full flexibility of solution chemistry can be exploited to make ceramic films and fibers with well controlled compositional characteristics. No less important is the ability to tune porosity and connectivity for specific applications such as optical and electrical coatings and membranes. Since the chemical and physical factors that determine the microstructure are not entirely understood, new diagnostics applied to sol-gel processing are welcome.Sol-gel films and fibers are distinguished by processing that takes a sol through continuous stages of increasing concentration and connectivity of a solid precursor. The liquid carrier is usually volatile or, at least, volatilizable through heat treatment. During deposition through states of increasing solids concentration, this sol might gel, as in bulk sol-gel processing, however, the gel state may be a fleeting transient that quickly empties of liquid. Nevertheless, the structures formed in solution during this stage influence the structure of the final solid. In particular, porosity is likely to be a remnant of networks formed in the sol-to-gel transition. Here we report on experiments whose goal is to discover the factors involved with porosity development."

Jan 1, 1994

By Z. Zhang, R. G. Reddy

The viscosities of industrial lead slags with various compositions were measured as a function of temperature. It was found that viscosities of lead slags decreased with increasing temperature, and the plots of ln(11) vs. 104tr followed a linear relation over the reported ranges of temperature. Using the data of this study and available other related data from the literature, a viscosity expression was developed as a function of composition and temperature. The calculated results using this viscosity expression are in good agreement with the measured data. The composition dependency of viscosity of lead slags is discussed.

Jan 1, 2000

By L. Deininger

The QSL plant in the existing "Betzelius" Stolberg GmbH lead smelter in StolberglGermany was commissioned in August, 1990. Following some modifications to the process and equipment which had become necessary in line with the implementation of this new techno- logy, conclusive operating results are now available. These will be reported together with a short description of the plant design. In May 1992, raw material feeding to the QSL reactor in the new lead smelter of Korea Zinc Co. in OnsanlKorea was started. As all the experience gained up to that point in time in the Stolberg plant had already been incorporated in this plant prior to start-up, it reached stable, satisfactory operating conditions in a short period of time. After an introductory description of the plant important operating results will be reported. The operating experience gained in the two plants fully confirms the correctness of the in- ventors' creative ideas in the 70s. The QSL process meets all demands made on modern, ecologically compatible and energy-saving lead production technology. The paper ends with suggestions on how the QSL process will be optimized further in the future.

Jan 1, 1994

By M. I. Kalashnikova

Gipronickel Institute has developed the technology of treatment of difficult to concentrate sulphide Pb-Zn concentrates (Zn-19,9%, Pb-8,4%, Cu-0,34%, Fe-8,8%, Ba-6,8%, S-18,7%, Ag-106 g/tonne). The technology consists of pressure leaching, impurity removal from leaching solution, electrowinning and Pb-Ag containing cake treatment. Despite low zinc content in initial concen-trate the technology allows production of solution which is suitable, after standard procedure of impurity removal, for electrowinning with production of zinc grade SHG. Comparing to the standard technologies the flowsheet developed provides the lesser expenses per zinc unit because of decreasing of liquid to solid ratio at pressure leaching stage. The initial concentrate is characterized along with low content of principal metals by high con-tent of barite, which makes flotation of pressure leaching residue more difficult. That is why in this case the hydrometallurgical treatment was chosen. At optimal parameters of chloride leach-ing found during laboratory experiments the principal components extraction was 99.5% for Pb and up to 92% for Ag.

Jan 1, 2006

By Luciano B. Oliveira, Alexandre M. Stumbo, Luis G. C. Marques, Valdo S. Marques, Sergio N. Monteiro

"Similar to the ethanol program, initiated more than 30 years ago, the recently created biodiesel program in Brazil is expected to rely on private initiative based on agribusiness for vegetable oil production. Campos dos Goytacazes is a large county in the northern of the state of Rio de Janeiro with land still available for oily vegetables plantation in addition to the land traditionally occupied by sugar cane plantation, which is used to produce ethanol. In order to extend the biodiesel program to Campos dos Goytacazes, the State University of Northern Rio de Janeiro (UENF) is conducting a technical project for the development of the infrastructure for biodiesel production. In this work, the infrastructure based on versatile equipment for biodiesel esterification built in the Center for Alternative Energy of the UENF is presented.IntroductionBiofuels are gaining worldwide attention as a possible economical solution for the prediction of declining reserves of petroleum and related increase in price of barrel. However, nowadays, a more relevant question is the climate changes caused by burning fossil fuels. This is especially the case of coal and petroleum based fuels, mainly gasoline and diesel that propel the majority of vehicles and generate a large amount of CO2 emissions responsible for global warming. This combination of economical an environmental problems is already providing a strong motivation to substitute conventional fossil fuels by renewable biofuels. More than just the interest of the market financial forces, government legislation is imposing a new order that obliges the use of biofuel. Many countries including the USA, the European Community, Japan and Brazil are committed to gradually substitute biofuels into their fleet of vehicles."

Jan 1, 2008

By J. L. Watson

The composite nature of titanomagnetites found on the west coast of the north island of New Zealand is an important parameter in the beneficiation of the black beach sands for export to Japan. To investigate this composite nature, borehole and plant samples from the Waipipi Ironsands Ltd property were subjected to a series of separations in heated Clerici solutions at densities varying from 3.2 to 4.6 g/cc. The resulting density fractons were analyzed magnetically and a set of distribution curves for composite grains proposed. In addition the experi¬mental data was plotted to produce titanomagnetite sand 'washability curves" which illustrate the possible problem areas in beneficiation that may arise due to composite titanomagnetite grains. From this data a set of guidelines are suggested for interpreting the curves in terms of ease of gravity concentration. The composite nature or liberation of titanomagnetite grains is shown to favor high and low grade composites with few intermediate compositions being isolated. The relationships between grain size, borehole depth and liberation are examined and related to beneficiation procedures for the black sand deposit.

Jan 1, 1982

By A. G. Cecutti

A brief overview of the known significant health effects of both Nickel and Cobalt will be presented. Some time will be given to the current research activities, especially for Nickel. Emphasis will be placed on some of the controversial issues associated with their health effects.

Jan 1, 1988

By Rina Kim

The addition of lead to a gold leaching reactor can effectively accelerate or retard the gold cyanidation reaction. This study explored the effect of lead on the gold dissolution kinetics using cyclic voltammetry (CV) experiments. It was illustrated that the gold leaching kinetics in the cyanide solution enhanced with the addition of lead salt in the low overpotential region (–0.35 V vs. Ag/AgCl). The similar behavior was observed in the presence of ore containing 0.25% galena. In contrast, the gold oxidation kinetics retarded at –0.35 V (vs. Ag/AgCl) in the presence of silicate and lead-bearing mineral under certain conditions. Likewise, the lead addition was not functional for the high sulfur ore. This was attributed to the oxidation of the sulfides to the elemental sulfur, which subsequently formed a passivating layer on the gold surface. The results were evidently affirmed by the electrochemical tests and X-ray photoelectron spectroscopy (XPS) analysis.

By Ravi Vancheeswaran

The consolidation of ceramic fiber reinforced metal matrix composites is a key process step in the synthesis of high performance composite systems. A simulation tool has recently been developed for predicting the evolution of the composites internal state microstructural variables (eg. relative density, fiber microbendinglfracture, and chemical reaction layer thickness at the fiber-matrix interface) during the consolidation processing of spray deposited composite mono-tapes. A Generalized Predictive Control (GPC) scheme is used in conjunction with the simula-tion tool to design near optimal process paths that minimize fiber damage and reaction product thickness while simultaneously maximizing the composites relative density. The microstruc-tural evolution depends nonlinearly on the process conditions and therefore the scheme uses a constantly updated linearization of the model to optimize the input process variable vector. A control simulation is presented to illustrate the performance of the design scheme and to assess the feasibility of its use for the achievement of goal state microstructures at the completion of consolidation cycles.

Jan 1, 1996

By Kirsi M. Riihilahti

The oxidation characteristics of solid copper matte particles under simulated Kennecott-Outokumpu Flash Converting conditions are presented. This project is concerned with the determination of the effects of operating variables on the reaction of the particles. Experiments were carried out in a large laboratory-scale flash furnace with 72 wt-% Cu matte by varying initial particle size, temperature, oxygen partial pressure, oxygen-to-matte mass ratio and residence time. Chemical analysis was used to study the oxidation extent and copper volatilization. Particle fragmentation was examined. Fractional conversion and sulfur removal slightly decreased with initial particle size, while a higher oxygen-to-matte mass ratio mainly resulted in higher fractional conversion and more efficient sulfur removal. The fractional conversion values represented the overall extent of oxidation more closely than degree of sulfur removal.

Jan 1, 1997

By Yuanbing Ling

Keywords: Calcium sulfate, Sulfuric acid, Phase transformations, Thermodynamic analysis As part of a boarder research project, seeking the development of a cost-effective process for direct production of the high value material, -calcium sulfate hemihydrate, from sulfuric acid at atmospheric as opposed to elevated pressure conditions, the fundamental work presented here has been undertaken. This includes experimental monitoring of phase transformation reactions and thermodynamic analysis of the relationships among the various phases, namely, calcium sulfate dihydrate, hemihydrate and anhydrite in aqueous sulfuric acid solution at temperatures ranging from 20oC to boiling point.

Jan 1, 2004

By C. S. Ek

As a continuation of previous work, further tests have been carried out to recover silver from the residues obtained in a zinc jarosite process. Selective flotation has been performed with different reagents, and ?cleaning steps have been introduced to upgrade the silver concentrate. Leaching of crude residues, as well as flotation tailings, has been carried out with cyanide and thiourea. Finally, the different beneficiation methods are compared, and the industrial aspects? of their application are reviewed.

Jan 1, 1990

By R. E. Sundell, S. M. Correa

"A mathematical model is developed for the fluid flow in tungsten-inert gas weld pools. The fluid is taken to be incompressible, viscous, electrically conducting, and confined within a pool of specified shape. The flow is driven by surface-tension gradient (thermocapillary), electromagnetic, and buoyancy forces generally in this order of importance. Analysis indicates that the electromagnetic field may be calculated a priori and so decoupled from the nonlinear fluid mechanics and heat-transfer problem. The resulting set of equations is solved numerically by a line relaxation process. Computational errors caused by truncation in finite-difference schemes and by inadequate grid distributions are considered. The model is used to study several cases of differing heat and current input to the pool with and without surfactant-induced thermocapillary forces. The principal conclusions are that the thermocapillary flow, when present, is dominant with surface velocities on the order of 1 m/s. The heat transfer, as deduced from isotherms within the pool, is crucially dependent on the flow. Also, flow velocities and weld-pool surface temperatures were measuredand agree well with the model.2. IntroductionThe requirements of improved control and of automation in the TIG (tungsten-inert gas) welding process have led to the development of mathematical models for the heat transfer to the workpiece. It is now widely recognized that the fluid flow in weld pools sufficiently distorts the conduction heat transfer pattern to warrant inclusion in a process model. The experiments of Woods and Milner (1), among others, demonstrated that TIG weld pools could be driven by the electromagnetic J x B body forces present, J being the current distribution and B the induced magnetic field. Atthey (2) calculated that in typical pools the buoyancy force was about an order of magnitude less important - despite the large temperature gradients present - and neglected it in a computational study of the magnetohydrodynamic (MHD) flow. This work also reviewed many earlier studies of MHD flow caused by a source of current at a fluid surface, including analytical studies by Shercliffe (3), Sozou (4), and Sozou and Pickering (5), and a numerical study by Andrews and Craine (6). These works establish the importance of the electromagnetic force in the weld-pool flow."

Jan 1, 1986

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 Y. Maeda

Kosaka Smelter is a copper smelter located at the nothern part of Japan? and has been treating. complex sulfide concentrates using flash smelting technology for a long time. The flash smelting technology has an advantage in the point of controllability of matte grade and heat balance in the reaction shaft. But the disadvantage of this process, is that the dust generation ratio is high compared with other smelting process such as injection smelting technology. This reason why is that the flash smelting process is the oxidation process for the fine sulfide concentrates applying flash reaction in the oxygen enriched stream In addition of this disadvantage, the sulfide concentrates contains much volatile impurities is resulted the dust; eneration ratio more. This paper outlines the recent improvement of the flash reaction in the furnace and the behavior of impurities in Kosaka Smelter.

Jan 1, 1998

By Courtney A. Young

All cyanide species are considered toxic and can be found predominantly in industrial effluents generated by metallurgical operations. For example, cyanide's strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent water contamination. Various methods of cyanide remediation by separation and destruction are available, but certain methods are more effective than others depending on the cyanide species being remediated. Photolytic destruction is regarded as the one technique that is independent of the cyanide species involved. The destruction of various cyanide species by several photolytic techniques has been investigated for the past few years. A literature survey suggests heterogeneous photocatalysis with anatase (TiO,) should behave similarly to homogeneous photolysis with hydrogen peroxide (H,O,) since proposed reaction mechanisms for both processes involve hydroxyl radicals. However, experimental evidence on a suite of cyanide species suggests otherwise. A new mechanism for the photocatalytic destruction of cyanides, especially SAD species, is therefore proposed.

Jan 1, 1998

By Junmo Ahn

This study investigated leaching kinetics by alternative lixiviants for copper leaching from chalcopyrite (CuFeS2), the most abundant copper resource in the world. As a refractory sulfide mineral, chalcopyrite shows low copper extraction due to passivation on chalcopyrite surface. Also, decrease of copper grade with high portion chalcopyrite requires the alternative leaching procedure to increase copper recovery. Therefore, alternative lixiviants such as sulfurous acid and methanesulfonic acid (MSA) were tested for both concentrate and low grade ore to enhance copper extraction. Also, an oxidant, hydrogen peroxide, was compared to ferric to find out the improvement of leaching kinetic. In concentrate leaching tests, 30 g/L MSA showed the highest copper extraction (47%), compared to other lixiviants at 75 °C. Periodical H2O2 addition enhanced copper extraction, and above 90% of copper extraction was observed within 96 h by periodical addition of 0.6% H2O2 at 75 °C. The activation energy of chalcopyrite leaching by MSA and H2O2 achieved 40 kJ/mol, which is chemical reaction control. The results of low grade ore leaching tests indicates that no significant difference among lixiviants (H2SO4, H2SO3 and MSA) with ferric was observed, all of which achieved around 37% within 24 h at room temperature. However, significant increase of copper extraction (>80%) was observed at both 20 g/L MSA and 10 g/L H2SO4 conditions by the addition of 10% H2O2.

By Mike Santaluce

Smelting furnace rebuild projects often require a significant capital expenditure and an extended smelter outage. Smelter operators are increasingly searching for methods and initiatives to shorten furnace rebuild schedules, maintain manageable cost levels, enhance furnace performance and achieve excellent safety results. This paper describes the ?MEPC? Model for furnace rebuilds; a project driven approach which Auburn has developed in response to the need for improving furnace rebuild project outcomes. The ?MEPC? (Management, Engineering, Procurement and Construction) approach better addresses the unique challenges presented by furnace rebuild projects when compared to the traditional EPCM (Engineering, Procurement, Construction Management) model widely in use for these projects today. One key feature of the MEPC model is that a dedicated project management team with representation from all of the major project stakeholder groups is put in place at the onset of the project. The project management team has ownership and accountability for meeting overall project goals over the entire lifecycle of the furnace rebuild project. A second key aspect of the model is emphasis on project management as a completely separate project function with its own specific skill sets, techniques, tools and best practices. These features of the MEPC model offer several advantages in terms of improved planning, coordination, communication and alignment with project goals which contribute to the overall success of furnace rebuild projects. Similar MEPC concepts have been used to deliver excellent project results in other industries and the MEPC approach has been successfully utilized on furnace rebuild projects.

Jan 1, 2006

By Sugui Tian

By means of the T6 treatment, the measurement of creep curves and microstructure observation, the influence of T6 heat treatment on the microstructure and creep properties of Ti-6Al-4V alloy is investigated. Results show that the microstructure of the forged alloy consists of the banded-like a phase and networks b phase. After sub-temperture T6 treated, the microstructure of alloy consist of the block a phase and ?networks basket? structure. Under the conditions of the applied stress of 575 MPa at 4000C, the forged alloy displays a lower creep lifetimes, after T6 treated the creep lifetimes of the alloy is enhanced to 548 h from 66 h, which is attributed to the formation of the network basket structure in which the needle-like phase are dispersedly distributed. As creep goes on, the denser dislocations in the a phase are concentrated to occur the dynamic recrystallization for refining grain. which is a main reason of the alloy displaying a better creep lifetimes and plasticity. Thereinto, the creep mechanism of the forged alloy is thought to be the slip of the straight <a> and <a+c> dislocation are activated on the prismatic planes and pyramidal planes, while the creep mechanism of T6 treated alloy is that wave-like <a+c> dislocations are activated on the pyramidal planes.

Jan 1, 2009

By W. Murray Small

Nickel plays an important role in determining the properties of many stainless steels and superalloys. Cobalt also contributes significantly to the performance of certain grades of superalloys. A major technical aspect, in which both of these metallic elements are involved, concerns the solubility of nitrogen in these classes of alloys. Beyond certain content limits, dissolved nitrogen may contribute to the deleterious mechanical behavior by these alloys. It is therefore essential to control the level of this element during alloy processing. In this paper, results from several experimental studies have been assembled and are analyzed to describe phenomena related to the individual effects of nickel and cobalt on the solution of nitrogen in several groups of alloys. Both solid and liquid alloy systems are considered. This information may be used as a guide to limit or control the presence of this interstitial element in alloys.

Jan 1, 1993