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By D. G. C. Robertson

The thermodynamics and kinetics of the reactions involved in fuming zinc from oxide slags using coal or coke were first studied in 1955 and have been the subject of many investigations since that time. The key reaction is ZnO(in slag) + CO = Zn(g) + CO2 This paper will review the some of the recent work, and will add new insights obtained in experiments carried out by the authors. In the first series of experiments it was shown that the reaction does not occur at an appreciable rate, as is expected from thennodynamic considerations. In the second series of experiments it was shown that zinc does not fume from the slag at a significant rate unless a reductant has been added. This again is in accord with thermodynamic considerations, but is in contradiction to some of the experimental results reported in the literature. A third series of experiments was carried out with excess coke being present, so that the rate of supply of reductant was not in any way controlling the rate. The kinetics of zinc oxide reaction were then found to be independent of the zinc oxide concentration, but increased with increasing basicity, and temperature. The presence of high concentrations of FeO in the slag also improves the kinetics. At low zinc oxide coneentrations iron oxide reduction occurred in parallel with zinc oxide reduction. We propose that (under the conditions of this work) the kinetics were controlled by a chemical step, namely the rate of desorption of an adsorbed CO2 species. This is the same mechanism as reported by Belton and co-workers for the kinetics of the reduction of FeO. This explains why the reduction of metal oxides in slags by hydrogen is often faster than by CO.

Jan 1, 2003

By C. M. Acuna

Scarcity of high grade copper low impurity content ores is a reality and processing of low grade dirty concentrates is a need. In spite of this fact, innovative strategies have to be looked at to comply with day to day more stringent environmental regulations. From this perspective the production of matte grades over 70% in copper presents several merits, but it must be contrasted with the fractional distribution of impurities reporting to the condensed phases. Converting of white metal high in arsenic content results in moderate fraction of arsenic to gas, but high deportment to blister. Therefore, production of anode copper, as required by the electrolytic refinery, may result in several operational difficulties. Furthermore, by recycling the flue dust and slag produced in the smelting-fire refining cycle, the arsenic content in the feed to smelting increases and so does in the resulting anode copper. The Teniente Converter, as a smelting unity, has probed suitable for production of high matte grade near white metal composition but regarding distribution behaviour of impurities there is lack of reliable data, specially when processing concentrates over 1% in arsenic content. In the new scenario, i.e. low grade copper high arsenic content concentrates, to fully asses the merits of this technology the effect of matte grade, secondary materials recycling and arsenic in feed upon the distribution coefficient of arsenic between slag and matte, mainly, must be evaluated both from a theoretical approach and by use of industrial data. Based on available data correlations of distribution coefficient, matte grade and matte/slag ratios with arsenic in feed and copper content in slag are worked out. Based on these results suggestions as to matte grades facilitating to deal more efficiently with the handling of smelting byproducts are proposed.

Jan 1, 2006

By M. Brian Maple

A rich variety of phenomena are produced by superconducting-magnetic interactions in rare earth and actinide compounds. These phenomena, and the materials in. which they have been observed, are described in this talk, with an emphasis on the new high superconducting transition temperature (Tc) copper oxides. The Materials The-materials in which these phenomena occur can' be divided into two classes. In the first group, there are two distinct interpenetrating systems of electrons, a set of localized 4f or 5f electrons and a set of itinerant electrons. The localized f electrons carry magnetic moments and interact with the spins and momenta of the the itinerant electrons, which are involved in the superconductivity, via exchange and electromagnetic interactions; respectively. This category includes materials containing rare earth (R) and actinide elements with partially-filled f electron shells which have been inroduced as substitutional impurities [e.g., La1-xCexA12, Th1-xUx] or form a sublattice in compounds [e.g., RRh4B4, RMo6S8, RMo6Se8, the high Tc. superconductors RBa2Cu3O7-d(d - 0.05)]. Materials of the second type are characterized by a single band of electrons that is responsible for both superconductivity and magnetic order. This group includes heavy electron rare earth and actinide compounds [e.g., CeCu2Si2, UBe13, UPt3, URu2Si2], and the high Tc copper oxide superconductors such as the hole-doped systems Lag- MxCuO4 (M = Ca, Sr, Ba, Na) and RBa2Cu3O7-d(0 =d= 1) and the electron-dope system Ln2-xMxCuO4-y (Ln = Pr, Nd, Sm, Eu; M = Ce, Th; x = 0.15; y - 0.02).

Jan 1, 1992

By Mitsuru Tanahashi

Oxidation removal of boron from molten silicon by injecting oxygen and highly basic CaO-CaF2flux powder has been investigated with special attention to the dynamic behavior of the injected flux particles and gas bubbles. Since oxygen gas is injected into the melt, high oxygen partial pressure is maintained at the flux-O2-Si interface and the removal of boron proceeds under nonequilibrium conditions. By applying this process, boron concentration in metallurgical-grade silicon can be reduced to a single-ppm level. In this paper, the effects of the dynamic behavior of the flux particles injected into the silicon melt and the area of the reaction field (the flux-O2-Siinterface) formed in the vicinity of the flux-gas exit of the injection nozzle on the rate of the boron removal are discussed from the viewpoint of process dynamics. The experimental results clarified that the boron removal rate is affected by the kinetic energy of the flux particles which is determined by the injection conditions, such as the gas-flow rate of oxygen and the size of the flux particles. At higher oxygen gas-flow rates, the injected flux particles are expected to possess a significantly high kinetic energy such that they penetrate the O2-Si interface formed at the nozzle exit, which results in the formation of a new reaction field for boron removal. On the other hand, at lower gas-flow rates, the injected flux particles possess too low kinetic energy to penetrate the interface. In this case where the formation of the reaction field is limited, it is shown experimentally that the rate of the boron removal is constant, independently of the flux injection rate.

Jan 1, 2006

By Yi Feng Shi

The ISASMELT process is a submerged lance smelting technology operating in smelters in Australia, the USA, Belgium, India, Germany, Malaysia and China. Further plants are under construction in Peru and Zambia. Initially developed at Mount Isa Mines, Australia, the technology is marketed by Xstrata Technology to companies around the world. Yunnan Copper Co. Ltd. (YCC) commissioned the first copper ISASMELT furnace in China in 2002. The plant quickly ramped up to design capacity and the first campaign lasted more than 2 years. Now into the second campaign, the furnace is exceeding the original design capacity and YCC has won numerous awards for its contribution to reducing emissions and energy consumption. YCC and Xstrata put great effort into managing the design, construction and commissioning of the smelter. Xstrata?s technology was combined with YCC?s novel management approach. This effort has been repaid in terms of the outstanding performance of the plant since startup. This paper updates the reader on the first few years? operation of the YCC ISASMELT plant and discusses the way in which the technology was transferred, leading to fast rampup and, as a result, enhanced profitability for the operators.

Jan 1, 2006

By Teruo Bitoh, Shogo Izumi

"The effect of B203 flux melting on the structure and the soft magnetic properties of the (Feo.1sBo.20Sio.os)96Nb4 bulk metallic glasses prepared by casting has been investigated. The ringshaped bulk specimens were prepared by the B203 flux melting and copper mold casting. It was confirmed that the flux melting promotes the precipitation of the a-Fe(-Si) and Fe2B phases in the central region of the specimens. The ring-shaped bulk specimens show a flat hysteresis curve, indicating a good linear relationship between the magnetic induction and the applied magnetic field. These results show that it is possible to develop a new soft magnetic material that exhibits constant permeability, which is necessary for producing inductors and choke coils.IntroductionSince the success of forming Fe-based bulk metallic glasses (BMGs) with good soft magnetic properties, great attention has been developed to synthesis and properties of the BMGs [l, 2]. The BMGs have high glass-forming ability (GFA) and, therefore, they can be used to prepare bulk amorphous alloys with a thickness of the order of a few millimeters by casting. The soft magnetic properties of Fe-based BMGs are better than those of ordinary amorphous alloys; therefore, these BMGs have wider applications as soft magnetic materials [3-5]. It is often required for soft magnetic materials that the shape of the hysteresis curve is changed according to the demands of applications. For example, materials with ""flat hysteresis curves,"" which means the magnetic flux density (B) and the applied magnetic field (H) show a linear relationship up to rather high magnetic field, are necessary for producing inductors and choke coils. Flat hysteresis curves can be easily achieved by creating an air gap in the magnetic path. However, magnetic flux leakage generated in the air gap inhibits high-density packing of the electronic components. In order to achieve flat hysteresis curves without creating an air gap, Fe-based ordinary amorphous alloys are subjected to crystallization by annealing and transformed into thin surface layers of a-Fe; the crystallization results in the compression of the remained amorphous phase [6]. Another way to achieve flat hysteresis curves is the formation of secondary phase (such as Fe2B) that act as pinning site of magnetic domain wall displacements [7]."

Jan 1, 2013

By Viktor. P. Popov, Oleksandr. V. Derev'yanko, Oleksandr. I. Raychenko

"This paper is devoted to scrutiny problem of obtaining electro-contacts by electro-discharge sintering technology. A new unconventional method of electro contacts production (on Aggraphite base) can yield essential optimization resource.Review of three electro-technological methods of processing contacts materials is presented:- using graphite powder cladded by Ag;- mixture of graphite powder(which is a non-cladded powder) with Ag powder and addition of Fe powder particles;- method of infiltration of melted Ag into graphite piece without deformation and rupture of object.This technological approach can give the possibility to increase of compression strength of electro-contacts materials up to 340 MPa and more under conditions of additional reinforcing components (for example, by Fe).IntroductionThe electric current can be an active ""participator"" of the powder metallurgy technology [l]. At the passage of electric current through powders or some powder mixtures the phenomena including phase transformations arise. Here such effects, which are observed in the Ag-graphite and Ag-Fe-graphite powder mixtures and in the pair Ag-porous graphite, are described.The Ag-graphite composition materials (CM) are used, for example, as electric contacts [2, 3]. Since a material being produced is destined for the contacts it is necessary to take into account the following aspects: commutating current, its character and voltage, active or reactive character of working load, geometrical dimensions of contacts, quantity and frequency of switching on and switching off, pressure on contacts, distance between contacts, method of arc control, surrounding medium, its content, pressure and temperature. Thus, these and, maybe, choice of some other circumstances influence design, materials and production technology of contacts. The range of problems concerned dictates such steps as alloying of contact materials, optimization of structure, selection of kind of graphite, its connection with metal [4-10]. It is expedient to recall the main procedures of the first stage of the conventional technology: dosage of the initial graphite powder and binder-phenolic resin plastic varnish (for example, Bakelite), mixing, densification, thermal treatment, crushing, grinding, sieving, drying, dosage of grained graphite, dosage of the initial silver powder, obtaining of the silver salt solution, settling of salt, filtration, washing, drying of the cladded graphite powder, thermal treatment, obtaining of the graphite powder of particles cladded by silver. The second stage of the convectional technology starts by obtaining of the cladded graphite powder and finishes by annealing of the pressed blanks (Fig. 1)."

Jan 1, 2004

By Renxing Li, Yongyong Gong, Yufeng Cheng, Zhenxing Yin, Xin Cao, Qijie Zhai

"This paper investigated the refinement effect of pulse magneto-oscillation (PMO) on the solidification structures of medium carbon steel S45C in metal mould. The induction coil was positioned at the middle of ingot. The results showed that solidification structure of the treated ingots was remarkably modified with a transformation from well-developed dendritic structures to small dendritic structures or globular structures compared to the untreated ingot. The area fraction of modified microstructure regions reached more than 80 percent. A further experimental investigation had been done to understand the influence of refinement effect on the solidification structure under different mould size. Theoretical analysis demonstrated that the mechanism for the refinement of solidification structure was that PMO promoted nucleation near the mould walls and changed the interface temperature gradient and concentration gradient in liquid, eventually leading to a transition from the columnar crystals to the equiaxed crystals.IntroductionIn recent two decades, the electromagnetic processing of materials (EPM) has been widely used in many fields such as ironmaking, steelmaking, and solidification processing [1-6], where EPM can control melt flow, modify melt shape, reduce macro-segregation and refine microstructure. Pulse magneto-oscillation [7-9] (PMO), as a novel technique of EPM, has a remarkable effect on grain refinement and high potentiality to be used in industrial production. Compared with ultrasound refinement technique, PMO can be easily employed to metal solidification processing for long time in no contact with hot metal liquid by using a water-cooled coil. Another important advantage is that PMO needs smaller energy compared to pulsed magnetic field which needs a very high current to obtain a strong magnetic field to get a satisfactory effect. These advantages mentioned above are beneficial for industrial application, which make it potential to be widely used in future. Gong et al. [7] have studied the refinement effect of PMO on pure aluminum and find that PMO can significantly modify the solidification structure of pure aluminum. Li et al. [9] have reported the effect of temperature field on solidification structure under the influence of PMO. On the basis of these works, this paper has studied the effect of PMO on solidification process of medium carbon steel S45C in a metal mould, which can also provide some information for industrial application of this new technique."

Jan 1, 2012

By Lucas Nana Wiredu Damoah, Lifeng Zhang

"Increasing demand for Solar Grade Silicon (SoG-Si) due to rising interest in renewable energy has lead to increased SoG-Si Top – cut scraps generated from the multi-crystalline silicon making process. Due to the high cost of SoG-Si and the potential to use the top-cut scraps as feedstock material, there has been increased effort to develop cost effective and efficient technologies. As a result, several methods to recycle the top-cut scraps are currently been applied, and researched. These include settling under gravitation field, which is a slow process to be industrially applicable. Natural settling of inclusions by gravitational force is a slow process and not attractive to the industry. Recent experiments on Top-cut SoG-Si scrap under high frequency, high voltage, electromagnetic field showed that SiC inclusions settled within a short time to the bottom of the crucible and the characteristic rod-like morphologies of Si3N4 inclusions in SoG-Si were not detected. This study investigates the enhanced settling of SiC inclusions and the behavior of Si3N4 particles under the influence of high frequency, high voltage, electromagnetic field in Top-cut SoG-Si.IntroductionThe photovoltaic industry depends on silicon based PV materials either as single-crystalline silicon, or multi-crystalline Si (MC-Si), or amorphous Si [1] for over 90 % of its market share. [2] MC-Si produced by directional solidification of solar grade silicon melt dominates the silicon PV market. During the directional solidification process, SiC and Si3N4 particles within the melt are pushed by the solidification front to the top of the ingot which is the last to solidify. Therefore the top of the ingot is cut generating what is known as top-cut solar silicon scraps. The Si3N4 particles are mainly from the coating material at the inside surface of the silica crucible and from air absorption during the solidification process. The SiC particles mainly stem from the carbon reduction process of the primary production of silicon [3]. Due to the growth of the PV industry as a result of global demand for clean, reliable, and affordable energy [4], there is the need to develop new methods to compliment exiting ones to recycle SoG-Si waste (e.g. top-cut) for sustainability."

Jan 1, 2012

By T. T. Natarajan, Nagy EI-Kaddah

"Numerical simulation of electromagnetic confinement systems generally requires large CPU time due to the strong coupling between the electromagnetic and the free boundary problems. The present paper examines the accuracy and the computational efficiency of the most common numerical schemes used in modeling such systems. Levitation melting was taken as a test case. In this study, a comparison was made between the finite element and surface integral methods for electromagnetic field calculations. The computational efficiency of Lagrange and the modified Hestenes methods for solving the free boundary problem were investigated. The convergence of the Lagrange method was found to be much faster than the modified Hestenes method. It was also found that finite element method not only gives accurate solutions, but faster convergence to the final equilibrium shape than the surface integral method. The applications and the limitations of these techniques in modeling electromagnetic confinement systems will be discussed.IntroductionIn recent years there has been a growing interest in the use of electromagnetic forces for confinement of molten metals as a means to eliminate molten metal contamination during melting and to improve surface quality of cast products. Continuous casting of metal without contact of a mold is now a reality, and is being commercially applied for casting of aluminum slabs /1/, and copper rods /2/. New applications of electromagnetic confinement in melting and casting include containerless melting (Magnetic Suspension Melting) /3/, edge containment in twin roll casting, and meniscus shape control in continuous casting of steel /4/.Modeling of confinement systems involves the determination of the electromagnetic field and the equilibrium shape. These two problems are strongly coupled due to the dependence of the field on the shape of the melt. While significant advances have been made in computational electromagnetics /5/, the application of developed computational techniques to electromagnetic confinement problems is not a simple task. The principal difficulty in using these methods is that the solution domain is not known a priori. due to coupling between the electromagnetic field and the free boundary problems. These two problems have to be solved simultaneously, leading to an iterative solution procedure. As a result, numerical simulation of electromagnetic confinement systems are computationally intensive with computational time at least an order of magnitude larger than the fixed domain problems."

Jan 1, 1994

By Bob Drew, Alfred Spanring, Kirschen. Marcus

"Increasing material conversion and energy efficiency, and decreasing carbon dioxide emission levels are crucial for sustainable production processes in the aluminum, cooper, and steel industries. RHI supports these targets by providing a diverse range of solutions including high quality refractory linings, optimum lining maintenance, and process improvements. In this paper examples are provided of process improvements and increased energy efficiency in copper refining, potential energy savings during electric arc furnace and ladle operations in the steel industry, and increased energy efficiency by improved heat transfer in anode baking furnaces in the aluminum industry. In all cases, RHI’s expertise in close collaboration with the customer resulted in an improved performance of the reactor lining and the actual high temperature process with a positive impact on the material conversion and energy efficiency and as a result a decrease in specific carbon dioxide emission levels.IntroductionRefractory linings play an important role in heat transfer during high temperature processes in for example the aluminum, copper, and steel production industries. Due to constantly increasing energy prices worldwide and the increasing demands for environmental and climate protection, improving the energy efficiency and decreasing emission levels of these energy intensive production processes is of significant importance. In this paper, the contribution of modern RHI lining technologies to energy saving measures and the corresponding reduction of specific carbon dioxide emission are described. The type of current refractory solutions for energy intense processes are illustrated with four examples: Optimization and increase of material conversion and energy efficiency in copper refining, energy saving potentials in both electric arc furnace and transport ladle operations in the steel industry, and heat transfer improvements during the carbon anode annealing process in the aluminum industry. These examples focus on particular production processes operating with a high proportion of recycled copper, steel, and carbon anodes. Increased energy efficiency directly decreases the specific energy related carbon emission levels whereas improvements to the metallurgical processes aim to increase material conversion efficiency and, therefore, decrease specific process related carbon emission levels. Significant energy savings can be achieved by maximizing the refractory campaign length through a combination of appropriate refractory material selection, grade zoning, correct installation, careful preheating, and effective maintenance strategies. Besides the efforts to improve the performance and energy efficiency of customer high temperature processes, RHI continuously promotes the development of new low emission carbon-containing refractory bricks and unshaped products."

Jan 1, 2008

By Roberto Giovanardi, Isabella Lancellotti, Luisa Barbieri, Ercole Soragni, Fernanda Andreola

"Recovery of precious metals (PMs) is a present topic, as they are used almost in every electronicelectric device. Gold is the second PM in order of consumption (following silver) and it is almost ubiquitary in electronics where it mainly finds application to produce bonding wires in integrated circuits and as a coating for contacts and connectors. Given this, discontinued electronic and, with a minor role, electric devices may represent a primary source of PMs as gold mines or jewelery wastes.At present the recovery of gold from such waste is generally accomplished by two strategies: by oxidative thermal treatment followed by metallurgical or chemical processes or by cyanide chemical etching; both techniques do not represent the optimum as the first one deserves a great amount of energy and non-combustible pollutant slag and fumes are produced, while the second procedure comports the use of a highly pollutant agent as cyanide.The aim of this work is the characterization of different electronics scraps to evaluate the gold concentration, and the selective recovery of this metal using enviromentally-friendly techniques. In particular, a new process was developed in order to overcome such environmental and efficiency issues. The process reaches the goal of detach the gold film from the substrate by selective leaching of the supporting metal.IntroductionThe treatment of waste from electrical and electronic equipments is a current topic as their role in modern life is increasing. The disposal of such waste represents both an environmental and an economical concern due to the vast amount of both precious and non precious metals.The use of precious metals (PM) in this field is of primary importance given PM’s unique properties, which give to each of them a specific and irreplaceable role. Silver is the most used, with a demand of over 5000 tonnes per year, mainly for switches and contacts in electric appliances. Gold is the second PM in order of consumption (over 250 tonnes per year and 8% of the total demand) and it is almost ubiquitous in electronics where it finds application to produce bonding wires in integrated circuits and as a coating for contacts and connectors. It is also used as solder in integrated circuits (in alloy with tin) or for wide coatings where it ensures protection against corrosion. Palladium, platinum, rhodium and iridium follow in order of consumption [1- 3]."

Jan 1, 2008

By M. Jortikka

The smelting process of the old reverberatory furnace including its capacity has been improved over the years in different ways eg. with oxy-fuel burners, parallel reactors with the reverb or with various modifications of the reverb furnace itself. The future reverb modifications with old concepts are difficult or impossible as the increased copper losses in slag call for separate slag treatment and particularly the process modifications do not solve the environmental issues but instead mean unavoidable high capital and operating costs in gas cleaning and sulphur recovery. During the last decades improvement in process performance and increase in capacity of copper flash smelters has been achieved easily by substituting the pre-heated process air by highly oxygen enriched air. The flash furnaces of today, however, are inherently designed to operate with high oxygen enrichment. Further process improvement with a view to production costs and capacity increase as well as to the more stringent environmental requirements is possible with even higher oxygen enrichment. This, apart from the advantages it generates, requires improvements in and careful design of the feed system, concentrate burner, furnace cooling and the off-gas line as well as adaption of the flash converting instead of the conventional Peirce-Smith converters. A logical answer even for the revamping of the reverb smelters in the future is the total replacement of the reverb furnaces with flash smelting together with flash converting. This paper discusses the possibilities for future process improvements of the existing flash smelters taking into account the process concepts, equipment modifications and capital aspects not forgetting the environmental issues. The revamping of the PASAR smelter in Philippines is introduced as an example of a recent success story.

Jan 1, 1994

By Vadim J. Jabotinski

Electron beam processing is potentially very attractive for the high temperature treatment of hazardous materials. The very high power efficiency of the electron beam energy source (80- 90% of the power from the electric power line is converted to useable energy) is one of the positive features of this technique. This paper will consider advanced electron beam concepts for solid, liquid, and gaseous waste treatment such as stabilization of radioactive solid and liquid hazardous streams. Fundamental aspects and applications including an analysis of the economic potential of electron beam processing of waste treatment will be presented.

Jan 1, 2000

By D. R. Spink

A partial desulfurization roasting (PDR) technique has been developed for use on zinc concentrates whereby the sulfide sulfur associated with the iron content is selectively removed over a very short residence ?time in the roaster. The resulting PDR product is then leached for the selective removal of the iron. The resulting leach restdite is an upgraded zinc sulfide concentrate which has a very low iron content. The up-graded zinc concentrate can be subjected to a conventional dead roast without formation of deleterious zinc ferrite so that hot acid leaching and jarosite (or other) iron precipitation steps are obviated. Examples are presented for the treatment of three very different types of zinc concentrates.

Jan 1, 1990

By Enrico Cerilli, Bryan Salt

Xstrata Nickel’s Sudbury Smelter has systematically developed its converting aisle from a single stage to a counter current multi stage converting process. This has required the development of two unique converters; the Slag Cleaning Vessel (SCV) and the Slag Make Converter (SMC). This has resulted in a unique three stage converting process that enables treatment of secondary materials and producing a slag that can be discharged without further treatment. The paper will also discuss future changes currently being considered to further improve environmental, plant hygiene and productivity performance.

Jan 1, 2009

By Yun Li

In 1999 Yunnan Copper Corporation (YCC) decided to modernise their copper smelter and change the existing sinter plant I electric furnace process to a combination of ISASMEL T and electric slag cleaning furnace. The main aim of the project was to improve the environmental performance and decrease the energy consumption. Generally the project has been successful, partly attributable to the selection of a reliable and fully demonstrated technology. The design capacity for the ISASMELT furnace is 600,000 tonnes of dry copper concentrate per year. The furnace has been running smoothly since heat up in May 2002. YCC expended considerable effort in the preparation for plant operation. An extensive training program for key YCC personnel at the Mount Isa Copper Smelter improved their understanding of the process significantly and ensured successful hand-over of the technology. This paper describes the project history and summarizes initial operating results.

Jan 1, 2003

By Yun Li

In 1999 Yunnan Copper Corporation (YCC) decided to modernise their copper smelter and change the existing sinter plant I electric furnace process to a combination of ISASMEL T and electric slag cleaning furnace. The main aim of the project was to improve the environmental performance and decrease the energy consumption. Generally the project has been successful, partly attributable to the selection of a reliable and fully demonstrated technology. The design capacity for the ISASMEL T furnace is 600,000 tonnes of dry copper concentrate per year. The furnace has been running smoothly since heat up in May 2002. YCC expended considerable effort in the preparation for plant operation. An extensive training program for key YCC personnel at the Mount Isa Copper Smelter improved their understanding of the process significantly and ensured successful hand-over of the technology. This paper describes the project history and summarizes initial operating results.

Jan 1, 2003

By Steven M. Puricelli

Sulfuric acid plants associated with smelters, have historically been an overworked and often neglected pollution control device. They could do little more than manage the wide fluctuations in gas flow and SO2 strength from the smelter. With the introduction of flash smelting, the picture began to change, but the fluctuating batch converters continued to dictate acid plant design. More recently, the commercial use of continuous converting processes utilizing high levels of oxygen enrichment has dramatically upgraded the SO2 strength and stabilized the gas flow to the acid plant. The SO2 gas now issues continuously and at concentrations that allow for compact and, cost effective acid plants. Relieved of the burden of excessive dilution air, the heats of reaction can also be recovered as medium pressure steam and used to drive a generator, making the acid plant a net producer of power and a valuable asset to balance sheets. This concept was put into practice at the Kennecott Utah Copper Corporation smelter modernization project, located in Salt Lake City, Utah. The new acid plant, which was commissioned in June of 1995, is a sophisticated, low environmental impact, energy producing plant, worthy of review. This paper examines the key features of this acid plant, such as controlling its tail gas, by catalysis alone, to an environmentally friendly, 100 ppm of SO2, while feeding the acid plant converter with an efficient 14% SO2. The acid plant is also a prudent steward of energy resources, recovering 220,000 lb/hr of 140 psig steam from process heat which is used to generate a substantial 20 MW of gross power. Also discussed will be some of the ongoing issues, such as handling of selenium and fluorine in the gas cleaning sections, as well as a review of some. of the problems that were identified and resolved. Today's modem acid plants, by necessity, are becoming a producer of quality, valuable products, making the acid plant an asset and not a liability. Plants like Kennecott are already gaining wider acceptance and are expected to be the vision of the future.

Jan 1, 1998

By B. G. Thomas

"Mathematical process models can be applied in several different ways to serve industry by inducing beneficial changes to process operation. This paper attempts to summarize the different uses, types, and attributes of these models, and to offer some ideas to consider when developing, using, and reporting on them. Process models range from empirical to mechanistic in nature and vary in complexity from simple analytical solutions to coupled, 3-D transient numerical simulations. They are classified here according to the way in which they are implemented in practice, viz. fully-online models, semi-online models, off-line models, and literature models. The purpose of the model should dictate how choices are made during its development. Ways to validate and compare the model with experiments are suggested. Examples are taken in the context of the author's experience in modeling the continuous casting of steel.IntroductionThe objective of this paper is to provide a partial introduction for this symposium by discussing some basic aspects of the application of mathematical process models in industry. Essentially, the aim is to explore how process models are used to benefit industry, and to offer some general comments and suggestions, based on the experience of the author, on how models can best meet this goal.This work is concerned with process models, which consist of systems of mathematical equations and constants that are solved on a computer to make quantitative predictions about some aspect(s) of the process. The specific variables required as input data and generated as output data are important features of the model. The equations often derive from a numerical solution to one or more differential equations and their boundary conditions. The model also includes the constants, which represent material properties, empirical relationships, and other knowledge about the process, and usually require considerable effort to obtain. Thus, general purpose commercial software packages, (ie. finite-element or finite-difference based codes), are not models in this context. They are useful tools, however, serving as frameworks for the development of process models."

Jan 1, 1994