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By Harvey Alter

National attention in, recycling focuses on municipal solid waste (MSW), even though only about 50'million tons or so of MSW can be recycled, including grass, leaves and other yard wastes. The scope and value of the recycling of industrial "wastes" is much greater. It is possible to account for some 240 million tons of material recycled at the industrial scale annually, which is likely a conservative estimate. Some of this recycling reduces what would otherwise be hazardous waste to 'comrnodities and non-hazardous residue. Global trade in recycled commodities is outlined, as well as the-effect of the Basel Convention on the Trans boundary Movement of Hazardous Wastes A recent Decision under the Convention can, diminish the trade; deny developing countries needed secondary raw materials, and put world markets in chaos. Current U.S. government policies and activities toward ratification of the Convention, and possible new regulation of industrial recycling activities, will be discussed. There are federal proposals that would regulate industrial recycling differently for on-site and off-site facilities and judge legitimate or "sham" recycling according to the concentration of so-called "toxics along for the ride."

Jan 1, 1995

By Mamoru Kuwabara

A high-power sound which can transmit through any continuous elastic medium with less attenuation, particularly in liquid allows us to externally control the system of concern by using the acoustic radiation force or the cavitation phenomena. These functions may eliminate gravitational and/or atmospheric constraints which are often encountered in conventional operations for producing clean and advanced materials. This paper outlines the recent development in the field of sonoprocessing of materials. Cold model experiments in some vessels have been performed to simulate ultrasonic operations such as inclusion removal from liquid, degassing of melt, emulsification of two liquid phases, solidification processing, and decomposition of chemical species in waste water. High speed visual imaging is carried out for better understanding of the cavitation phenomena as well as the followed microjets during the processing. The radiation force acting on fine suspending objects in a fluid can be utilized for eliminating or rearranging/orienting the objects in the fluid. Acoustically induced cavitation phenomena in liquid can be utilized as an effective dynamic means to control interfacial phenomena as well as micro- and macro-mixing of liquid. Sonochemical and thermal effects in cavitation multi-bubble can be also useful in a waste water treatment.

Jan 1, 2006

By C. Zografidis, K. Karalis, E. Devlin, S. Tabouris

"The main parameters affecting energy and electrode consumption in smelting reduction of Greek nickeliferous laterites in submerged arc electric furnaces (E/F) were investigated. Within this framework, the operational data of E/Fs, such as energy consumption indicators, electrode consumption indicators and chemical characteristics of Fe-Ni and slag, were correlated with the physicochemical characteristics of the calcine, produced by roasting reduction of laterite in rotary kilns (R/Ks), such as reduction degree, temperature, chemical composition and granulometry. The results obtained provide a significant input for further research on the modelling of the roasting reduction – smelting reduction process, which is a critical tool for energy optimization.IntroductionThe two main steps of pyrometallurgical treatment of greek nickeliferous laterites for ferronickel production include: i) drying, pre-heating and controlled pre–reduction of laterite ores with solid fuel reducing agents and fuel oil in rotary kilns (R/Ks) for the production of a calcine, and ii) smelting reduction of the calcine in open-bath submerged-arc electric furnaces (E/Fs) for the production of Fe-Ni alloy with 12-16% Ni [1].The energy absorbed from the endothermic reductive reactions of iron, nickel and cobalt oxides (Fe2O3, FeO, NiO and CoO) of the calcine with the remaining carbon in the E/Fs, corresponds to about 16% of the total energy output in the smelting reduction step [1]. This is indicative of the significance of the calcine’s reduction degree for the electric energy requirements in the E/Fs. Moreover, the chemical characteristics and the granulometry of the calcine constitute critical parameters for the energy requirements as well as the smooth operation of the E/Fs."

Jan 1, 2012

By Leonel Contreras

The gas treatment system, MALIGAS (in Spanish MAnejo y Llmpieza de GASes which means handling and cleaning of gas), is part of the Codelco-Chile Potrerillos Smelter decontamination plan; which includes the newly designed system for the cooling and cleaning of the gas generated from a Teniente Converter and four Peirce Smith Converters. The gas generated in the process is captured by water cooled hoods and mixed with air. Then the gas enters a cooling pre-chamber which utilizes a water cooled screen to capture and remove the coarse and semi-fused particles. At this stage; the gas loses a portion of its heat with temperature falling below 608°C which is a necessary condition to avoid damage to the pipes, ducts and other metallic structure of the gas handling system. The gas is further cooled at the Radiation Cooler to a temperature ranging between 315 and 380°C. The gas is conditioned to avoid damage to the electrostatic precipitators that are designed to clean the gas by removing significant amount of dusts from the: gas stream. This gas stream is currently discharged to the stack, however, it will be treated in a sulfuric acid plant that is currently under construction and is scheduled for commissioning during the second half of 1999. The gas handing and cleaning system has been operated without any significant interruptions. Minimal emissions of SO2 and dusts in the work place are noted. The system requires minimum maintenance. The key to the high availability of the system is due to the good, performance of he Radiation Cooler, which efficiently cools the gas before entering the electrostatic precipitators (ESPs). This enables the ESPs to remove the dusts efficiently.

Jan 1, 1999

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade.

Jan 1, 2006

By A. M. Strachan

The arising and behavioural pattern of polonium-210 in the Capper Pass & Son Limited non-ferrous metal smelting and refining circuit is briefly discussed. The process developed for the removal of polonium from lead, solder and bismuth is discussed in detail, together with the essential personnel safety and environmental protection precautions which must be taken during the refining and subsequent storage of the active dross.

Jan 1, 1992

By Robert W. Hyers

Electromagnetic levitation has proven important in a wide range of experiments, all affected by fluid flow. For some experiments such as viscosity measurements, only whether the flow is laminar or turbulent must be established. For other experiments, however, quantitative assessments of velocity, shear stress, or shear strain rate are required. In most cases it is difficult or impossible to measure the internal flow in levitated droplets directly. The samples are usually small, opaque, reactive, high-temperature, metastable, or all of these. Furthermore, recirculating flow limits the utility of tracking surface particles, since they collect in stagnation points ratherthan following the flow. Most research groups have chosen mathematical modeling to assess the internal flow in levitated droplets. A variety of analytical and numerical methods have been applied, including both laminar flow and various turbulence models. A number of these models are reviewed and their impact on different containerless experiments is assessed. Much of the research reviewed here was performed by alumni of Professor Julian Szekely, and by others using similar methods.

Jan 1, 2006

By G. A. Brooks, R. W. Matusewicz, Nazmul Huda

"A computational fluid dynamic (CFD) model of a conventional tuyere blown slag fuming furnace has been developed in Eulerian multiphase flow approach. The model was developed by coupling CFD with kinetics equations developed by Richards et al. for zinc fuming furnaces. The model integrates submerged coal combustion and chemical reactions with the heat, mass and momentum interfacial interaction between the phases in the system. The model predicts the velocity, temperature field of the molten slag bath, generated turbulence, vortex and coal utilization behavior from the slag bath. The highest coal penetration distance was found to be at l/L = 0.2, where / is the distance from the tuyere tip and L is the total length (2.44m) of the modeled furnace. The model also predicts that 10% of the injected coal bypasses the tuyere gas stream un-combusted and carried to the free surface, which contributes to ZnO reduction near the free surface.IntroductionSignificant metal values are often discarded with slag in the form of metal oxide produced by the smelting industries. These metal values can be recovered from the slag by proper treatment. Zinc slag fuming is such a process, where a reductant source (usually coal) is injected in the molten slag bath to reduce dissolved ZnO from the bath into metallic zinc vapour. The process can be carried out in either conventional tuyere blown furnace or top submerged lance (TSL) smelting furnace. Conventional slag fuming processes are carried out on batch basis in a rectangular tuyere blown furnace. Approximately 50 tonnes of charge (either molten slag or solid slag) is fed to the furnace at the beginning of each fuming cycle. Two opposing sets of submerged tuyeres are employed to inject air and pulverized coal into the molten slag bath to carry out combustion and reducing reactions."

Jan 1, 2012

By Nagahiro Saito, Takashi Nishimura, Takamichi Ichikawa, Akio Fuwa

"Yttria-stabilized zircohia (YSZ) has high potential to be used as solid-oxide fuel cell (SOFC) electrolyte. However, the high efficiency of SOFC has not been yet achieved due to the high internal resistance of bulk electrolyte. The resistance becomes lower with the decrease in the electrolyte thickness. Thus, the decrease in electrolyte thickness leads to lower internal resistance. . The aim of this study is as follows: (a) to prepare the thin films of YSZ by inductively-coupled RF plasma-enhanced metal organic chemical vapor deposition (PEMOCVD) process using Zr(t-OC4H9)4,Y(DPMh and oxygeil, and (b) to reveal the relationship between the structural characterizations and the process parameters.1. IntroductionYttia-stabilized zirconia (YSZ) has, been widely used as not only heat-resistant materials but also the components in automotive oxygen sensors, electrolytes of solid-oxide fuel cell (SOFC)(1)(2) and the buffer layers for the high-temperature superconductor because of its low thermal conductivity, good mechanical properties and high ionic conductivity. However, it is said that the internal resistance of the bulk electrolyte is too high to be appropriate as a solid electrolyte for high-efficient SOFC. The authors believe that the thin YSZ electrolyte can give a high performance to characteristics SOFC, since the internal resistance becomes lower with the decrease of electrolyte thickness. Thus the process technology to prepare YSZ thin films is desirable and must be established.In recent years, the YSZ thin films have been reported by chemical vapor deposition (CVD), thermal CVD using metal chlorides (MC) of ZrCl4 and YC(3)(4), thermal CVD using metal organic compounds (MO)(5)(10) Zr(t-OC4H9)4 and Y(C11H19O2)(11) and plasma-enhanced (PE) CVD using MO. Here, these methods are called MCCVD, MOCVD and PEMOCVD. MCCVD has two disadvantages; a large quantity of chlorinated impurities in deposited films and high processing temperature (> 1273K). This high processing temperature leads to damage of substrates in particular, so the application of this technology is limited. On the other hands, the processing temperature by MOCVD becomes and is lower. Unfortunately, the accurate vapor pressures of these metal organic compounds have not been, known so: that it is difficult to control the composition and the film thickness by MOCVD method well. Moreover, the large amount of carbonic compounds in the films prepared by MOCVD method is produced. However, plasma-effect has been reported to decrease large amount of the carbonic impurities by PEMOCVD. However, PEMOCVD has many reaction parameters in plasma processing; the geometry of experimental apparatus, radio frequency, electronic power input and so on. Thus, the general understanding about the relationship among reaction parameters, the composition and crystal structure of thin deposit film by this method has not yet been established."

Jan 1, 2000

By Marshall Khan

The Goodfellow Expert Furnace System Optimization Process (Goodfellow EFSOP?) is a proprietary process that uses real-time and continuous off-gas analysis, along with process monitoring to optimize the operation of electric arc furnaces (EAF) for steelmaking. With the exception of off-gas composition, dynamic process measurements within the EAF are not possible due to the harsh operating environment. The Goodfellow EFSOP? system provides a dynamic indication of the operating conditions within the EAF. Continuous measurement of furnace off-gas composition, along with other furnace operating parameters is used to elucidate the fate of chemical energy usage within the EAF including: the evolution of carbon from the molten steel bath; the in-leakage of air into the furnace; the extent of combustion above the molten steel bath and the occurrence of dangerous water-leaks from the furnace cooling system. The ability to measure the process reliably and continuously enables Techint Goodfellow Technologies Inc (TGTI) to implement dynamic process control of combustion within the electric arc furnace and to optimize the overall operation through adjustments to the EAF process based on off-gas measurement. This paper discusses the methodology and results achieved from several recent Goodfellow EFSOP? installations in South East Asia.

Jan 1, 2006

By Rod Samuels, Rupert Allen, Thomas Harper

"Viceroy Resource Corporation of Vancouver, B.C., has recently developed and brought into production the Brewery Creek Mine, an open-pit heap leach gold mine, located 55km east of Dawson City in Yukon, Canada. Mineable reserves are 15.2 million tonnes of ore grading 1.45 grams/tonne, containing 22 tonnes (707,315 oz) of gold. Ore processing employs the heap leach technology using run-of-mine ore. Highlights of 1996 activity included construction of a 158,000 m2 of leach pad, placing 1.9 million tonnes of ore at a grade of 1. 46 gpt to the leach pad, construction and successful commissioning of the ADR plant, and pouring of the first gold bar on November 15th.Permitting of this mine has drawn significant attention because of the innovated heap leach technology; although this technology has been proven in other jurisdictions, it has not been used at such extreme northern sites where winter temperatures routinely reach -45°C for extended periods.ABSTRACT ONLY"

Jan 1, 1997

By Henrique Ventura Oliveira

Continuous casting is the most important process for solidification of steels. In this process, the fluid flow pattern in the tundish and in the mould have significant effect on the product quality. Problems associated to fluid flow in the tundish include surface turbulence, ?short-circuits?, formation of dead zones and vortexing. During grade changes, mixing in the tundish plays a significant role in determining the length of the intermixed slab. All these flow aspects can be studied by means of mathematical and physical models. In the last years, numerical simulation of fluid flow has become a very popular tool in the analysis of the performance of continuous casting tundishes. In setting-up these numerical simulations, special care should be taken in choosing the appropriate mesh distribution, the interpolation scheme, the adequate location of the inlet boundary and the turbulence model. In the present paper, turbulent fluid flow in different configurations of tundishes was simulated. Different turbulence models were used in the simulations. Residence time distribution (RTD) and mixing curves during grade changes were predicted and compared to results obtained in physical models. The performances of the different turbulence models were evaluated. For the tundishes that have been studied, the performances of the different turbulence models tested in the present work were similar. There is no evidence that any of the models provided sustained improvement when compared to the well-established standard k- model. All turbulence models tested presented limitations in simulating flows under low turbulent Reynolds numbers.

Jan 1, 2006

By Jitka Jandová

In this study, hydrometallurgical processing of waste ZnO flue dust arising during zinc removal from galvanized low-alloy steel sheets was investigated on a laboratory-scale to obtain electrolytic zinc. The flue dust was separated from flue gases, generated during heating waste galvanized steel sheets in an electric furnace under air atmosphere at temperatures of about 1000oC. The dust, comprising tetragonal ZnO and insignificant amounts of SiO2, was contaminated by Fe, Mn, Pb, Al, Mg, Pb, Cu and Ca. The dust was leached in 0.5 and 1.0M H2SO4 and/or in 20 and 30% NaOH at different temperatures and different liquid-to-solid ratios to determine the optimum conditions leading to the highest possible selectivity of leaching and efficiency of Zn extraction in minimum time. The subsequent electrowinning process was performed with refined zinc sulphate leach liquors and/or with untreated zinc caustic solutions. Zinc sulphate leach liquors were purified using a combination of a hydrolytic pH-controlled precipitation, cementation and carbon refining. Effects of operational variables on Zn electrowinning have been studied for both sulphate and caustic electrolytes. The conventional plate-plate electrowinning cell has been explored in this study. Comparison of results obtained for both zinc electrowinning from acid sulphate and alkaline solutions is presented contribution.

Jan 1, 2003

By R. W. Smith

The flotation response and electrokinetic behavior of Chlorella vulgaris and Chlamydomonas sp . when using dodecylamine hydrochloride as collector were studied in the absence and presence of Pb(I1). Also, an electron microscopy study was made of the algae after Pb accumulation. The flotation behavior of the organisms after Pb accumulation appears at least partially related to the location of the abstracted Pb onto or into the organisms.

Jan 1, 1991

By C. Cánepa

In the treatment of many problems related with the optimization of a given ore dressing process, microscopic studies can provide invaluable assistance. Such studies are generally carried out through mineralogical determinations both qualitatively and quantitatively. Frequently the solution of a specific problem requires the combination of these in adequate proportions. Often the nature? of the problem poses some conditions regarding the way the microscopic determinations are made in order to yield useful information. Most publications applied to mineral beneficiation show results of ore microscopy without mentioning the methodological details involved in the determinative work and therefore it is not possible to judge their reliability and/or their relevance. As methodology must necessarily change from case to case, it is very important for the microscopist to identify first the direct and indirect mineralogical information required to solve the problem. Without such guidelines selection of methods for the qualitative and/or quantitative determinations cannot be made.

Jan 1, 1981

"An experimental study has been performed to investigate the dispersed phase holdup induced by a high-strength submerged gas injection in a bottom blown air-stirred one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor using two different tuyere configurations. The air flow rates varied from 0.00599 m3/sec to 0.01312 m3/sec. In these series of experiments, water height and kerosene height were kept constant at 0.23m and 0.02m respectively. The dispersed phase holdup was determined at various gas flow rates, and tuyere orientations by using water and kerosene.The dispersed phase holdup increased with gas injection rate and decreased with vertical distance from the original interface. At constant gas flow rate, as the vertical distance increased in the centerline, off-center configuration of nozzles displayed higher values of the dispersed phase holdup than those of the center configuration. The variation of the dispersed phase holdup with the dimensionless axial distance and the gas injection rate was correlated by using the Modified Froude Number. The experimental values of the dispersed phase holdup were found to be in good agreement with the calculated values obtained from the correlation equations."

Jan 1, 1999

By R. Mehta, M. Misra, X. Su

"The conventional methods to assess Acid Mine Drainage (AMD) potential of the waste rocks and tailings are based on wet chemistry and leachability tests. These methods are time consuming and expensive. There is a growing interest to develop alternate techniques to establish the reactivity of acid mine tailings and stability of treated waste forms. The Electrochemical Impedance Spectroscopy (EIS) is a reliable non-invasive technique which can be used for quick estimation of reactivity of the potential acid generating tailings. In this paper the utilization of the EIS technique for the estimation of reactivity of tailings is discussed. EIS can also be used to predict the long term stability of different stabilized waste forms.IntroductionMetal contaminated mine drainage is one of the most persistent environmental problems facing the mining and mineral processing industries today. Of all the mine drainage pollutants, acid mine drainage has become a substantial concern because of the potential long-term environmental implications and the accompanying liabilities. The main source of acid mine drainage is the tailings containing sulfide-ores which are generated during the ore processing. When these sulfide minerals, particularly pyrite and pyrrhotite, are exposed to oxygen and water they begin to oxidize. The initial chemical reactions produce acid and the acid dissolves heavy metals present in the tailings. Rainfall and snow-melt flush the toxic solutions from the waste sites into the downstream environment [1-2]. In addition to mining tailings, several Department of Energy (DOE) sites contain wastes which are contaminated with radionuclides and heavy metals."

Jan 1, 1999

By G. Brooks, J. Naser, M. A. Sattar

CFD models have been developed and numerical simulations have been carried out to predict the formation of foam in oxygen steelmaking. Foam was considered as a separate phase comprising a mixture of gas and liquid. Bubble break up and coalescence models have also been incorporated in a CFD model to predict the number density of individual bubble classes. A population balance equation was used to track the number density of each bubble class. Decarburization with heat generation from chemical reactions was integrated in the process. User subroutines were written in FORTRAN to incorporate the foam formation, the bubble break up and coalescence rate and decarburisation in the main program. The model predicted the foam height, bubble number density, velocity of phases, decarburization, and turbulence. The result from the model has been compared with available data from literature and found to be in reasonable agreement with the experimental and plant data.

Jan 1, 2014

By Ramasamy Santhanam

"India’s present annual marine fish catch is 2.9 million tonnes and its low value fishes such as sardines, sciaenids, goat fishes and leiognathids amount to 60%. The fish meal obtained from these resources is mainly used presently as an ingredient in live stock and aquaculture feeds. These fishes offer vast scope in the production of pet foods. Pet foods prepared with leiognathid fish meal (60%), maize flour (10%), wheat flour (5%), vitamin and mineral mixture (5%) and water (20%) and experimented with 50 cats and 50 dogs were found to be ideal. Depending on protein level, feeds are being formulated for experimenting with more number of pet animals. Training programmes are also planned for unemployed people to popularize pet foods for commercial purposes.IntroductionIndia’s present annual marine fish catch is 2.9 million tonnes and low-value fishes sucha s sardines (Sardinella albella, s. gibbosa, S. fimbriata and S. melanura); sciaenids (Otolithus spp. and Jhonius dussumieri); engraulids (Stolephorus indicus); and leiognathids Leiognathus bindus, L. equilus and Gazza achlamys) constitute 60% (Figure 1)[1]. The fish meal obtained from these resources is now mainly used as an ingredient in livestock, poultry and aquaculture feeds. Considering the rich nutritional status of these low-value fishes, it is felt that these resources could be converted into value-added products viz. pet foods."

Jan 1, 2008

By Teruo Tanabe

The hydrogen-absorbing materials are expected to have the following properties at moderate conditions, (a) a large capacity of hydrogen absorption, (b) the absorption rate of hydrogen is large and (c) hydrogen-absorbed materials can easily desorb hydrogen. Thus the three concepts of capacity, rate and reversibility seem to be indispensable to clarify the mechanism of hydrogen absorption by the materials. In this work, the amount of absorbed hydrogen, the absorption rate and the reversibility of hydrogen absorption- desorption reaction were measured for binary R-M systems (R = Y, La, Ce; M = Co, Ni). These experimental results were discussed by the following three physical properties that were calculated by the extended Hückel method, i.e. the density of states unoccupied by electrons, the cohesive energy and the energy fluctuation. The major results are as follows: (a) the amount of absorbed hydrogen increases with the density of states in the energy range between -9 and -4 eV, (b) the R-M compounds of which energy fluctuations are large show a large value of rate of hydrogen absorption, and (c) when the cohesive energy is large, the compound has a tendency not to easily desorb hydrogen, i.e. its reversibility is poor.

Jan 1, 2006