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By Tan Pengfu

By using computer-aided techniques of equilibrium calculations for multicomponent and multiphase systems, a computer model has been developed to simulate QSL, KIVCET and Outokumpu flash lead smelting processes. A mathematical description is studied using two zones or three zones, namely smelting zone and slag reduction zone for QSL furnace, or offtake shaft zone, smelting shaft zone and electric furnace zone for KIVCET furnace. The amount of each component in lead, slag and gaseous phases under equilibrium is calculated by using the data of free energies of formation and activity coefficients. The predictions by the present computer model are compared with the known data from QSL-Plant at Korea Zinc Co. in Korea, KIVCET-Plant at Nuova Samim Co. in Italy and Outokumpu Co. in Finland. The agreements between the computer predictions and the known data are excellent, so that the present computer model can be used to monitor and optimize the actual industrial operations of direct lead smelting.

Jan 1, 1998

By Michael J. Nicol

This paper summarizes some of the results of a study of the reactions involved in the Caron leaching process and identifies the roles of the major dissolved species in the kinetics of dissolution of iron alloy particles formed during reductive roasting. Using rotating disk electrodes and synthetic leach solutions, the reduction of water with the evolution of hydrogen was found not to occur on a dissolving iron surface under typical leach conditions. It has been established that the oxidative dissolution is governed primarily by a reaction involving reduction of Co(III) to Co(II) ions. The reduction of oxygen was also found to make a significant but largely indirect contribution to the kinetics of the dissolution process. The dissolution rates of various iron-nickel-cobalt-copper alloys which simulate the dissolving alloy particles in a Caron plant were measured in synthetic leach solutions under aerobic and anaerobic conditions. The initial dissolution rates of iron, nickel and the iron alloys were found to increase in the presence of thiosulphate, whereas the thiosulphate had a negative effect on the dissolution rates of cobalt and copper. It is shown that the eventual passivation of the iron occurs sooner in solutions rich in Co(II) ions. Whilst these conditions are present in the quench slurry, on-site measurements have shown that due to the very high concentration of reduced dissolved species, passivation does not occur until the slurry is strongly aerated. In the light of these fundamental findings, options for optimizing the rate of dissolution and minimizing the extent of passivation of the iron and iron alloys are discussed. Keywords: Ammonia, leaching, alloy, kinetics, passivation.

Jan 1, 2004

By Mikio Kobayashi

Extraction of valuable metals from sulfide ores continues to be a very important, process and so the strict control of discharge of harmful metals in effluents from refineries becomes more important in the future. The recovery methods for heavy metals have been developed. Some metals such as Se and As are still difficult to be removed to very low concentration, although the techniques for recovery and removal for many kinds of heavy metals have already been developed. Especially, in case of Se the recovery system from water with low concentration has not be developed yet, although the WHO decided Se to be harmful for human beings and then the discharge control is under obligation now. In general Se exists as selenite ion and/or selenate ion in aqueous phase and selenite ion is able to be recovered by coprecipitation with ferric hydroxide or by reduction to solid selenium by general reductants. Selenate ion, however, has a strong resistance to conventional treatments. Therefore the new technique for the recovery of Se from water including selenate ion has to be developed. In this presentation the new approach for removal of selenate ion using the reaction in which ferrous ion is oxidized to ferric ion is presented. Selenate ion is reduced to selenite ion during the reaction and then to solid selenium, while ferrous ion is oxidized to ferric ion. The coexistence of activated carbon is very useful to increase the reaction rate. The use of iron powder is also effective and very useful for reducing gel-like precipitates mainly consisted of ferric hydroxide. The concentration of the residual selenate ion is probably under 0.1 ppm after recovering Se by the mentioned-above approach. In addition to the mechanisms of these reactions, the effects of pH, coexistent positive and negative ions, and reaction temperature are also presented. Furthermore the investigation of the behavior of selenosulfate is presented.

Jan 1, 1998

By Yongfeng Jia

Lime neutralization and co-precipitation of As(V) with iron(III) is the most widely used and most economical method for the removal of arsenic from mineral processing solutions and effluents. However, the arsenate fixation mechanism in the coprecipitated solids is not fully understood. It was suggested by various researchers to be a ferrihydrite precipitation process during which arsenate is removed by adsorption on ferrihydrite. In this study, XRD, EXAFS and microprobe were employed for the speciation of arsenic and the effect of various factors on arsenic solubility was also investigated. The results indicate that coprecipitation is a more complicated process than simple adsorption resulting in lower arsenic solubilities. Poorly crystalline ferric arsenate was observed for the first time to be present in the coprecipitated solids. In case of lime as base, there exists some type of Ca-Fe-arsenate association. A general term ?coprecipitate? is suggested to describe the precipitated arsenic-bearing solids instead of those widely used specific terms ?arsenical ferrihydrite? or ?arsenic-bearing ferrihydrite?.

Jan 1, 2005

By Geir Wedde, Anders Sorhuus

"Vast quantities of energy are released as heat to the environment from industrial operations. Many countries target waste heat recovery to mitigate CO2 emission. Exhaust gases from industries such as primary aluminium smelting, carry a substantial portion of the waste heat generated. For a cost efficient capture of more valuable heat (higher exergy), heat exchangers should operate on the exhaust gases upstream of the gas treatment plants. Heat exchange surface would be exposed to dust laden gases with risk of fouling. Heat exchangers of innovated design and operation have overcome the potential of excessive fouling rates. Heat exchangers of the ""shell and tube"" design have been demonstrated for exhaust gases from ferroalloy as well as primary aluminium smelters. In addition to the heat recovery, gas cooling results in smaller gas treatment plants with lower costs and reduced emission. The aluminium experience is exampled in the paper.IntroductionIndustrial usage of energy continues to grow as a result of increasing volumes of production, a trend that is likely to continue in the coming decades as living standards keep rising globally. World energy consumption (Figure la) is to grow 49 % by 2035 (ref. 2010) as reported by EIA [1]. The industrial sector consumes somewhat more than 50% of the total world energy consumption predominantly the energy increased demand comes from non-OECD countries in Asia. The industrial consumption by production of metals iron and steel accounts for 14 % and for non-ferrous metals 3 % mostly for aluminium production (Figure lb). Aluminium production will be discussed in this paper as an example of an industry with large quantities of waste heat to recover"

Jan 1, 2012

By Bret Boster

Facilities at Amax Gold's Sleeper Mine process some 330 kt of high grade ore and 4100 kt of low grade ore annually to produce 6.8 t of gold and 7.8 t of silver. High grade ore is processed in a conventional milling facility employing gravity concentration, CIC and CIP unit operations for gold and silver recovery. Low grade ore is processed using heap leaching and carbon adsorption methods.. Presented are the evolution and descriptions of the Sleeper processing facilities and discussions of selected' operating results.

Jan 1, 1989

By Baicheng Liu, Houfa Shen, Wensheng Li

"In order to understand the formation of macrosegregation in steel ingots, a mixture model has been developed which accounts for coupled mass, momentum, species, and energy transport to describe the sedimentation of free equiaxed grains during solidification. In this model, the mushy zone is divided into the slurry and porous regimes according to a solid packing fraction. Settling velocity of equiaxed grains in the slurry regime is given by an explicit expression. The solidification of a binary steel ingot (Fe-0.36wt.%C) with a two-dimensional geometry is numerically simulated. It is demonstrated that the predicted macrosegregation patterns agree to some extent with classical experimental results. Further refinement of this model is still necessary for realistically simulating steel ingot solidification.IntroductionModeling macrosegregation in steel ingots is still a challenging study, mainly due to the length scale of the products and the complexity of global multiphase transport phenomena coupled with microscopic solidification kinetics [l]. The thermal-solutal convection and the motion of equiaxed grains are the two main mechanisms responsible for macrosegregation. But there are few models that deal with the motion of equiaxed grains, which is confirmed as the main phenomenon that explains the negative macrosegregation along the centerline of large steel ingots [2]. A model which takes into account melt convection and grain sedimentation was first proposed by Beckermann and co-workers ([3], and references therein). More recently, similar multiphase solidification models with advanced nature have been presented by Wu and Ludwig [1,4] and Combeau and co-workers [5,6]. It is known that the application of these sophisticated models to steel ingot casting is at its beginning.In this paper, a solidification model based on continuum mixture approach, using much less sophisticated relations to obtain the settling velocity of free equiaxed grains, has been proposed in order to predict the macrosegregation in steel ingots. The model is applied to simulate the solidification of a binary steel ingot with a two-dimensional geometry, and preliminary modeling results are presented."

Jan 1, 2011

By Saskia Duyvesteyn

Small ion-exchange resin particles provide faster mass transport than conventional-sized beads. Unfortunately, high pressures are needed to pump solutions through columns containing small resin particles. It is preferable to disperse fine resins in the solution being treated. Screens have been used to separate the resin from the solution, but screens do not retain fines created by attrition of the resin particles. We have developed a separation process based on flotation, which relies on the surface characteristics of the resin, instead of size. The resin is conditioned with a surfactant before dispersing it in the solution to be treated; this increases the hydrophobicity of the resin sufficiently for froth flotation, without introducing surfactant directly into the solution. The surfactant adsorbed on the resin surface does not appear to impair the kinetics of metal ion removal. A flowsheet for an effluent treatment process is proposed; other applications are clearly possible.

Jan 1, 1998

By A. M. Alfantazi, M. Boissoneault, D. B. Dreisinger, J. Synnott

Acid mist generation is a major concern in zinc, copper and nickel electrowinning industries and there is a strong environmental drive to control its emission into the work environment. Foaming reagents are typically added to the electrolyte to alleviate this problem. In zinc electrowinning, Licorice and Saponin are examples of foaming reagents used for this purpose. In order for the foaming reagent to be effective, its foaming behavior must be determined. In this work, a test procedure was developed to study the foaming characteristics of various surfactants for use as foaming agents to control acid mist in aqueous metal electrowinning. This new test was termed as "mini-flotation test" and it was used to study the foaming behavior of a large number of reagents in an industrial zinc sulfate electrolyte under simulated zinc electrowinning conditions (gas sparging). In addition, the influence of important process parameters such as current density, electrolyte temperature, reagent addition level and sulfuric acid concentration on the foaming characteristics of the electrolyte for each surfactant were investigated. The results of this study have identified the most important factors that influence foam formation, growth and stability. This method could be used as a process control for reagent addition in the cellhouse by generating a calibration curve for the optimum electrolyte conditions.

Jan 1, 1997

By F. J. Tavera

Recently Jameson cell technology has gained acceptance in both mineral and non-mineral applications, mainly because of the high degree of contact between the involved phases in the downcomer, fact that leads to an efficient collection performance. The key for an acceptable performance of the downcomer operation depends on the stability of the jet zone, the mixing zone, and the plug flow zone. in this work the behaviour of the downcomer of a laboratory Jameson cell is reported, as a function of gas hold-up, superficial gas velocity, superficial liquid (or slurry) velocity, and length of the operating zones. The presence of carbon is evaluated in terms of its effect on the gas hold-up and bubble surface area flux. The influence of the downcomer operating conditions on the gas-liquid disengaging cell is presented. Keywords: Jameson cell, downcomer, gas hold-up, mixing, plug flow, conductivity.

Jan 1, 2003

By Takeshi Yoshikawa, Kazuki Morita, Yuichi Kato

"A composite composed of carbon fiber and a Cu-Si alloy is a promising candidate for next generation brake disc materials used in high-speed trains. The composite can be prepared by vacuum infiltration of the Cu-Si alloy into the fibrous carbon matrix. The activity of Si in the alloy plays an important role in controlling the formation of SiC; this formation is attributed to the reaction between the Si in the alloy and the carbon fiber during the infiltration process. Because Fe has strong affinity with Si, the addition of Fe is expected to decrease the activity of Si in the alloy. In the present work, the variation in the activity of Si in the alloy with the addition of Fe has been investigated by equilibrating a Cu-Fe-Si alloy with solid SiO2 and graphite under controlled CO partial pressure. The first-order and second-order interaction parameter of Fe on Si in molten Cu was determined to be -16 and 160, respectively. The negative value of the first-order interaction parameter clarified the addition of Fe to the Cu-Si alloy is effective in decreasing the activity of Si in the alloy.IntroductionIron-based materials have been commonly used for brake discs in high-speed trains. It becomes critical for brake disc materials to withstand high thermal loads with an increase in the maximum speed of high-speed trains. The fabrication of high heat-resistant, light-weight brake disc materials is then crucial for their use in next-generation high-speed trains. Carbon fiber is known to be a light-weight, high-strength material, and is considered to be a promising matrix material for use in brake discs. The Cu-Si alloy exhibits high thermal conductivity. The composite in which the Cu-Si alloy is added to the carbon fiber matrix is expected to be a high performance material for brake discs. The composite can be prepared by the infiltration of the Cu-Si alloy into the carbon fiber matrix at a temperature higher than 1700 K."

Jan 1, 2012

By J. S. Lee

A new high performance adsorbent is synthesized by the sol-gel method and applied to the removal of cadmium and mercury ions from aqueous solutions. Adsorbents based on metal oxides have been developed by immobilizing chelating molecules on the surface of the existing metal oxide networks and show ability for selective metal extraction from aqueous solutions. However, efficiencies of such adsorbents are limited due to low ligand density, and difficulty in pore accessibility. These difficulties are circumvented by synthesizing adsorbents using the sol-gel technique. In one example to be discussed, the sol-precursor possesses an organic moiety that binds cadmium, mercury, and copper ions. The capacities of 1.98mmol Cd(II-/gm and 6.40 mmol Hg/gm of this adsorbent are considerably higher than those of adsorbents prepared by the ligand immobilization technique. The scope of this paper is to discuss the development of the new adsorbent and its applications for cadmium and mercury removal from aqueous solutions.

Jan 1, 1999

By Jiang Fan, Wang Haigang

"The three-dimensional complex multiphase turbulent flow in U-beam separators was simulated using the Reynolds stress equation models (RSM). To account for the effect of the stochastic characteristic of the instantaneous gas velocity on the particles, the improved Lagrangian stochastic model based on the Reynolds stress model for gas phase was adopted, which attributed to the successful prediction of the turbulence anisotropy and particle crossing trajectories effects. The interaction between the particles was also considered using the HardSphere model. To treat the particle-wall collision, the influence of the roughness of the wall on the motion of the solid particles was taken into consideration by imposing random collision angles. The result from this study not only shows the dynamic characteristics of the multiphase flow- in the separators, but also gives the relationship among the efficiency, structure and pressure losses of the separator.IntroductionCirculating fluidized bed (CFB) combustion is one of the most promising clean coal techniques. A main feature of CFB boilers is the un-delayed recycle of solid, coal and sorbant particulate, in an external loop. Separator, which is required to separate the solid particle from the flue-gas leaving the reactor of CFB, plays an importance role in the external solids recycle loop. It affects the combustion of CFB system greatly. Presently cyclone is the most commonly used as separators for CFB system and other chemical industrial processes. It provides high level of separation for CFB system for fine particles. However it suffers from some inherent disadvantages. It's volume and size is huge. Moreover, it is difficult to design and install when the CFB workload rises. The application of U-beam separators instead of hot cyclone separators in CFB boilers has many advantages. Publications indicate proposals or successful use of Ubeam separators in Swedenr11, USA 21, Russia r3land China [4]• But it is not possible to find results in the literature of detailed investigations of this new. type of separators or recommendations on the choice and calculation of an optimal design. For this reason, numerical simulation for the three-dimensional gas-particle two-phase flows with several rows of vertical U-beam elements, local in the chess order and blocking a way of outgoing from a CFB boilers dusted gases was carried out in this study."

Jan 1, 2004

By Toshihiko Emi

The quest for cleaner steel is driven by increasingly stringent requirements from the manufacturing and construction industries. Key issues are the occurrence and removal of inclusions; These are discussed in the context of the unit processes of deoxidation, refining, transfer and casting of molten steel. Process thermodynamics and kinetics are also discussed. Recent progresses achieved and problems yet to be solved are elaborated, and an integration of the unit processes into a system to produce extra clean, steels with better performance is presented.

Jan 1, 1999

By Stephen M. Testa

Several methodologies are available for the remediation of contaminated soils including bioremediation, vapor extraction, chemical fixation, incineration and direct disposal. A proven innovative and cost effective alternative for the fixation of contaminated soils is via cold-mix Environmentally Processed Asphaltm (EPA"'). EPAm methodology utilizes contaminated soil as an ingredient in an industrial process to produce a commercially viable product. Petroleum hydrocarbon and metal affected soil is incorporated with a water-based asphalt emulsion and varying amounts of aggregate to produce a range of cold-mix asphaltic products that fulfills the requirements of a variety of end uses. This viable and creative use which is within the intent and spirit of current regulations in producing, in lieu of a landfill waste, an end product for use as a berm, road base, liner, or other site specific application. Consideration of certain engineering and environmental factors including durability, stability, chemical resistance and ageing, biological resistance, permeability, leachability and geochemical aspects suggests that cold-mix asphalt incorporation of affected soil will perform more than adequately under normal conditions for a long period of time.

Jan 1, 1994

By J. M. Figueiredo, A. R. Silva, M. C. Coelho, R. M. Guedes

"With the continuous depletion of conventional sources of non ferrous metals, low grade complex sulphide deposits have been regarded as an alternative source of supply of zinc, copper, lead and also silver and gold. In spite of very important efforts in research in this domain it is still a long way to go in order to achieve reliable technological solutions both in ore dressing and metallurgical treatments which enable these complex materials to be regarded as commodities. The RLE process to treat bulk concentrates such as those obtained from portuguese ores, under development at LNETI and QUIMIGAL premises, combines experienced unit operations and innovative configurations and is an effective contribution for the future use of these materials. The results of three years of experimental work and main conclusions on the overall feasibility of the process are presented.IntroductionIn spite of the very well-known problems associated to the development of complex sulphide deposits, the economical importance of the enormous reserves of these materials, widespread all over the world, is so evident that its future use as source of supply of basic and precious metals and other minor elements is almost unavoidable.Critical steps in that direction are mainly concerned with favourable economical conditions and sound metallurgical practice for the treatment of nonferrous metals concentrates, which are nowadays still considered as non-conventional raw materials.Since Portugal is one of the countries where these orebodies occur more extensively, Portuguese authorities have dedicated since the beginning of the seventies, a big effort on finding economical and reliable processes for the recovery of copper, lead, zinc and also gold and silver, and for this purpose, several alternatives on ore dressing and metallurgical processing were studied, however without full sucess.Five years ago LNETI, a research laboratory, and QUIMIGAL, a chemical company, both state owned, decided to launch a research programme for the development of a metallurgical process for the treatment of NFM concentrates, which received financial support from NATO under its programme ""Science for Stability""."

Jan 1, 1988

By Susumu Okabe

Mitsubishi Continuous Copper Converter employs the top blowing lance system for the continuous supply of reaction gases into the molten bath. In order to avoid the excessive refractory wear caused by the melt splash without loss of the reaction efficiency, the furnace design and the blowing condition should be optimized. Empirical equations which correlate the splashing rate on the' side wall with the dimensions of the furnace, lance position, lance size, gas velocity and bath properties were obtained by by the physical model study, and compiled into a computer program. The computer program is effectively utilized for the analysis of the actual operation and for the optimum design of new furnaces.

Jan 1, 1998

By K. Fagerlund

In this work, the rate of dissolution, melting behaviour and phase separation of silica flux with molten slag and matte were investigated. Mutual dissolution between high-grade matte and silica was chemically determined. Silica dissolution rates ,in various iron silicate slags was determined using the rotating rod method. The reaction and separation phenomena of slightly oxidised chalcopyrite samples and cuprous sulphide-magnetite mixtures with silica sand were examined all about 1350°C. The samples were water quenched, and polished specimens were studied and analysed using a light optical microscope ,and a scanning electron microscope with energy dispersive spectrometer. The silica dissolution rate in slag was found to increase with decreasing silica content and increasing ferric iron content. The reaction rate of silica sand' with matte was found to increase with increasing oxidation degree and magnetite content of matte:

Jan 1, 1998

By T. Shibasaki

There is a strong demand in the photo industry to the higher quality of refined silver. Osaka Refinery produces about 27 mtpm of refined silver mainly from copper refinery slimes. Product quality is attained by controlling the impurity level in electrolyte. Copper is cemented with silver oxide and palladium is precipitated by a chelating agent. Both processes were operated previously in batchwise for treatment of bled out electrolyte, Recently these processes have been improved and made continuous to cope with the increased impurity.load. As a result the grade of fine silver has been maintained steadily at Pd < 3 ppm and Cu < 5 ppm.

Jan 1, 1989

Gas flow and heat transfer phenomena in two industrial-scale waste-heat boilers of the Outokumpu copper flash smelting process were analyzed with a commercial computational fluid-dynamics (CFD) package Phoenics. Various operating conditions were simulated for the first boiler and particularly for the second boiler. The gas flow pattern was compared qualitatively with the physical laboratory models, and the general flow pattern was consistent with the laboratory visualization. The heat transfer simulation was validated with, temperature measurements for both boilers, and good agreement was reached between the computed temperature profiles and the measured data. The computational results indicate that gas flow in both boilers is of three-dimensional and recirculating nature. The numerical tracer experiments indicate that some dead volume is present in both boilers, and the boiler modification reduced the dead volume from 38% to 15% under basic operating conditions. Radiative heat transfer accounts for 65-90% of the total &apos;heat transported in the radiation sections of both boilers under different operating conditions. The modified boiler is very efficient for cooling the off-gases at almost doubled volume flow rate. The CFD modeling proved to be a useful tool for numerical experiments and analysis of boiler performance for process: optimization.

Jan 1, 1998