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By W. -D. Schneider, B. Schwab

Like all metals, zinc can be recycled theoretically without end. To demonstrate environmentally friendly use of zinc, it is necessary to increase the recycling rate. In this regard, the Imperial Smelting Process developed in the forties and fifties in the United Kingdom has become more and more important. This unique process combined with a sinter plant, hot briquetting, and direct injection through the ISP furnace tuyeres offers ideal possibilities to recycle all kinds of zinc and lead bearing materials. Possible secondary materials include Electric Arc Furnace (EAF) dust, zinc-containing sludges and even zinc/carbon batteries. This high temperature process also destroys all organic materials, like dioxin, and can be seen as a sink for many harmful substances.

Jan 1, 2000

By Akira Yazawa

In the field of pyrometallurgy, the equilibrium evaluation has recently become easy by use of thermodynamic software, but it is strongly desired to estimate the amounts of non-equilibrium minor components to simulate practical processes. However, simple physico-chemical technique can not be applied to evaluate practical non-equilibrium components for many reasons. As an engineering solution for postulated equilibrium system, the activity coefficient is modified and introduced as the simulation parameter referred to as the "adjustment coefficient." This modified thermodynamic calculations were adopted to various sulfide roasting processes where many solid phases are participating and the system is not necessarily in equilibrium. Successful simulation was realized by assigning suitable adjustment coefficients for minor components which form a pseudo solid solution in the calcine. Some examples from sulfation roasting and dearsenizing roasting were discussed. In the smelting system, the loss of copper in slag is caused by equilibrium and non- equilibrium reasons, that is, chemical dissolution and entrainment of copper in slag. The total copper content of slag was simulated by use of the adjustment coefficient for entrained copper.

Jan 1, 1998

By R. Hamar, G. Lamanthe

"To realize complex shaped pieces, like turbine blades, superalloys are cast with the lost-wax process. The end properties of these parts depend upon their microstructure as well as upon the occurence of casting defects such as micropores and hot tears. Such features are governed by the local solidification conditions which may be describe by the calculation of thermal transfers between alloy and mould. It needs the evaluation of numerous parameters which are fitted from experimental measurements in real castings. In further simulations, any parameter may be changed, in order to determine its influence. Such a single modification is quite impossible to realize in real castings, which shows that numerical modeling is a very good way to study casting processes.This modeling technique of casting is applied here to the real study of a typical low pressure turbine blade of a civil engine.IntroductionAircraft engine manufacturers use superalloys to produce turbine blades. They have to obtain a given microstructure and to avoid solidification defects to give good mechanical properties to theirs castings. For example, microporosity is induced by a large shrinkage that cannot be completely fed with the remaining liquid alloy .The optimization of casting processes needs a good Knowledge of the solidification process, that must be controlled at every place in the casting, and at every time of its freezing. Material and heat transfers that occur during the solidification, can be estimated from rather complex calculations. To model these physical phenomena, the evaluation of many parameters must be made. In this aim, some casting experiments are fitted with numerous thermal captors. The identification of experimental and computed thermograms let us estimate these parameters.A long-range scientific cooperation between SNECMA and INPG has enabled the realization of such studies on this topic. From all of them, this paper describes an experimental and computed investigation which has been led on a typical low pressure turbine blade of a civil engine."

Jan 1, 1986

By Mohamed Y. Bakr, Aly M. Abdel-Rehim

The present work is related with mechanical activation of processing of Egyptian wolframite by simultaneous ball-milling and pressure alkaline leaching, to improve the recovery of tungsten from wolframite. The results show a total recovery of tungsten from wolframite (97.8- 98.7%) by simultaneous ball–milling and alkaline leaching at temperature 175-200oC. It is concluded that processing of wolframite by simultaneous ball- milling and leaching is mechanically activated and accelerated as a result of the grinding action of steel balls that caused the immediate rupture by continuous removing the product layer of the reaction ( sodium tungstate and iron and manganese hydroxides ) from reacting particle surfaces. This leads to the exposing of fresh and activated wolframite particle surfaces to alkaline leach solution and consequently the acceleration of the reaction of wolframite leaching .The results of the kinetic study 0f alkaline processing of wolframite and its mechanical activation show that the system is under kinetic control.

Jan 1, 2015

By J. R. Donald

Electric arc furnace (EAF) dust, which can be considered as a by-product of the steel recycling process, contains significant quantities of recoverable zinc and iron, as well as hazardous elements such as cadmium, lead and chromium, which can be leached by ground water. The zinc in the EAF dust is found almost entirely in the form of either zinc oxide or zinc ferrite, the latter accounting for 20 to 50 percent of the total zinc. It is important that an efficient process be developed which renders the dust inert, while reclaiming the valuable metals to off-set processing costs. During the conventional carbothermic reduction processes, iron is formed, and this iron can participate in the reduction of the zinc oxide in zinc ferrite. In the present work, the reduction of the zinc oxide in zinc ferrite by iron according to the following reaction: ZnO-Fe2O3(s,s) + 2 Fe(s) = Zn(g) + 4 FeO(s) was studied in an argon atmosphere using a thennogravimetric technique. First, a thermodynamic analysis was performed using the F*A*C*T computational system. Then, the effects of briquette aspect ratio (lid), temperature, zinc ferrite particle size, amount of iron added, as well as additions such as lime, sodium chloride, and calcium fluoride were investigated. It was found that, initially, the reaction was chemically controlled with an activation energy of 178.1 kJ/mol. Then, after a product layer had formed on the outer surface of the briquette, the reaction was restricted by the diffusion of zinc gas away from the reaction interface. The parabolic rate law was fitted to the experimental data, and the parabolic rate constant was found to be: = -6.2275 + 0.0054 T (K)

Jan 1, 1995

By W. G. Davenport

The remainder of this book develops and uses mass and heat balances to describe steady"state flash smelting. Its objectives are to: a) describe the many ways a flash furnace operator can produce specified products, e,g. 65% eu matte, 35% SiOz slag, 1500 K (b) determine the oxygen, air, flux and hydrocarbon fuel requirements of each method (c) show how the flash furnace can be controlled to give specified products with varying feed compositions (d) suggest how the flash furnace operator can maximize profitability while producing specified products. This chapter develops the basiC heat and mass balance equations of steady-state ?flash smelting. It then adapts the equations to industrial feed materials .and products. Lastly it determines the amounts of oxygen and flux needed to produce molten matte and 35% SiOz slag from chalcopyrite concentrate in an Inco oxygen flash furnace,

Jan 1, 2001

By Denise Cristina de O. Nascimento

Natural lignocellulosic fibers are increasingly being used as polymeric matrix composite reinforcement owing to economical and environmental advantages as renewable and biodegradable materials. Among these, the piassava fiber extracted from a palm tree native of South America stands as one of the most rigid with a potential to be used as composite reinforcement. Therefore, the present work investigates the notch toughness behavior, by Izod impact tests, of epoxy composites reinforced with up to 40 % in volume of continuous and aligned piassava fibers. It was found that the incorporation of piassava fibers results in significant increase in the impact energy of the composite. Scanning electron microscopy analysis showed that the nature of the piassava fiber interface with the epoxy matrix is the major responsible for the superior toughness of the composite.

Jan 1, 2009

By K. R. Robilliard

The Peru based tin mining company, Minsur S.A., commissioned Ausmelt Limited to design, supervise construction and commission a tin smelter and refinery for production of refined tin metal. The plant is located 240km south of Lima, near Pisco, Peru and is operated by Funsur S.A., the wholly owned subsidiary of Minsur S.A.. Selection of the Ausmelt Technology followed a series of crucible scale test work and pilot plant trials conducted at Ausmelt's facility in Dandenong, Australia and two feasibility studies undertaken by Ausmelt in 1991 and 1993. Ausrnelt began the plant design in 1994 with the construction phase following in 1995. Commissioning of the plant commenced early in 1996 with a target throughput of 30,000 tonnes per annum of concentrates. In mid 1998 oxygen enrichment of the Ausmelt lance air was introduced to expand the capacity to the throughput of 40,000 tonnes per annum of concentrates. The process route involves the use of an Ausmelt furnace for primary concentrate smelting, followed by a conventional tin pyro-refining circuit to produce high grade tin suitable for sale. Further work continues between Ausmelt and Funsur to investigate the use of an alternative, more economical, fuel source and the installation of a second Ausmelt furnace. The paper reviews the project to date with details of ongoing operations and developments at the Minsur Tin Smelter.

Jan 1, 2000

By H. Shang

The materials science and metallurgical engineering communities have expended enonnous resources in developing high fidelity process models. Exploiting these Models for Predictive Optimization (MPO) and Control (MPC) is a new frontier in Materials Process Engineering that will lead to exceptional process perfonnance. This paper will begin with a short survey of the development of high quality process models available in the literature and a discussion of how these could be used to improve process operation. A summary of the current "state-of-the-art" in process automation technologies and the traditional framework in which these technologies are deployed will be presented. An illustration of the use of MPO in process design and operations will be presented for the continuous casting of steel. In addition, a simple run-out table simulation will be used to demonstrate the power of the MPC technique.

Jan 1, 2003

By I. Gaballah

Jarosite contains up to 15 % of heavy metal compounds 'HMC'. The current waste disposal methods will not be allowed in the near future due to new environmental regulations and pollution risks. For these reasons, thermal treatments of raw or decomposed jarosite, in controlled atmospheres, were investigated. The aim of these treatments is to decontaminate the jarosite and/ or to recover the HMC for recycling. According to physico-chemical characteristics of the samples, the thermal treatments in controlled atmospheres N2, CO+N2 and C12+air lead to the extraction rate that vary from 93 to 98 %. Heavy metal compounds were separated by cooling the gaseous phase. The treatments' residue was almost free from HMC. Between 700 "C and 800 "C, the chlorinating treatment was successful of eliminating more than 97 % of HMC contained in four different samples.

Jan 1, 1999

By Guohua Bai, Yuanbo Zhang, Guihong Han, Zijian Su, Daoyuan Zhang

"Specularite ores have poor hydrophilicity and ballability as well as inferior high-temperature reactivity, which restrict the large-scale application of them in the pelletizing and sintering production. Modified humic acid (MHA) organic binders are firstly used for pellet preparation from specularite in this paper. The results show that the drop strength of green pellets is 3.7 times/0.5m and compression strength is 12.5 N/P by using 1.0 wt% MHA as binder. Under the optimal experimental conditions of preheating temperature 980 °C, preheating time 12 min, roasting temperature 1280 °C and roasting time 10 min, the preheated pellets have the compression strength more than 400 N/P, and that of roasted pellets is 2747 N/P. The strength of finished pellets meets the requirements of blast furnace iron-making. MHA is a kind of more effective organic binder for specularite pellets compared with the inorganic bentonite.IntroductionAcid Pellets have advantages of good strength, uniformity particle size, high iron grade and good reducibility, which can be used as high-quality burdens for blast furnaces [1]. With fast development of Chinese iron and steel industry domestic magnetite concentrates with high grade of iron and good firing performances become shortage.Imported specularite ores have advantages of low price and high grade of iron (generally above 67 wt%), so the application of them in pellets is an effective way for sustainable development of pellet industry in China. However, the specularites have not been utilized in pelletizing and sintering at present because of the poor ballability and high-temperature reactivity [2, 3]. Most of the pellet plants use bentonite as binders, the amount of which is about 2~3 wt%. The pellet production practice shows that 90 wt% bentonite is still residual in finished pellets and reduces the iron grade [3]. Developing a new organic binder instead of bentonite is very important to the high-quality pellet production. On one hand, the consumption of bentonite is obviously reduced, resulting in decreasing the ironmaking coke ratio and slag discharge; On the other hand, the iron grade of finished pellets are improved, which brings the benefit for the ironmaking production."

Jan 1, 2011

By Kotaro Ogura

"Ethylene has been produced in aqueous solution from CO2 by the electrochemical reduction driven by a natural energy. This process is useful for storing a large amount of the natural energy. In the closed system, the conversion efficiency of CO2 is almost 100%, and the maximum selectivity for the formation of ethylene is more than 70%. On the other hand, the current efficiency for the competitive reduction of water is less than 10%. The electrolysis is practicable under such special conditions as three-phase interface consisting of gas, solution and metal, concentrated solution of potassium halide, low pH and copper or copper halide-confined metal electrode. These requirements are thoroughly examined, and the grounds to reply upon are revealed. A series of chemical apparatuses including an electrolytic cell in a large scale are designed for the ethylene production, which allow us continuously to supply raw CO2 and to extract the product.IntroductionIn connection with the depletion of the petroleum reserve, much attention has been paid to the utilization of natural energies such as sunlight, wind force and waves. However, these energies are always changeable, and some means of storing them are necessary for the common use. In general, natural energies are transformed to the electric energy at the time of utilization, but the electricity is not very storable. This is one of the reasons why the application of natural energy is not so expanded. On the other hand, the storing of natural energy by plants is very skilful. In the photosynthesis, solar energy is transformed to chemical energy by fixing carbon dioxide."

Jan 1, 2009

By Francis C. Furman

Microscopic evidence indicates that the high sinterability of certain commercial dolomites is tied to specific dolomite textural characteristics. This study encompasses detailed characterization of the unprocessed dolomite and sintering doloma results. The chemical and mineralogical compositions, insoluble residue, chemistry homogeneity, crystal size, primary carbonate texture, secondary dolomite texture, deformation structure, porosity type, porosity, and density of the raw dolomite were observed. These characteristics are compared with sintering trials of <74um powder-compacts samples in which holding times were varied. The evolution of the dolomite characteristics are reviewed and related to the final sintered doloma characteristics. The critical characteristics of a single-stage sintering brick dolomite are the following: 1) primary oolitic texture, 2) dolomite purity, 3) dolomite stoichiometry 4) minimal impurities, less than 1 weight {%} Fe2O3 Al2O3 and SiO2, 5) chemical homogeneity, 6) high density, 7) very low porosity, S) very coarse homogeneous crystallinity, 9) nonplanar dolomite texture, 10) abundant strain related slip microdeformation structures, 11) minimal subsequent alteration. Even with grinding to <74um the nonplanar dolomite texture and slip deformation still have a major effect on doloma sintered density. The three newly identified characteristics of single-stage sintered refractory brick dolomite are their primary oolitic texture, secondary nonplanar texture and abundance of stress related microdeformation structures. The primary oolitic texture reflects a homogeneous pure carbonate with respect to chemistry and crystal size secondary nonplanar texture produces crystals with large surface area to volume ratio. Stress related slip deformation moves CO, groups in to the same site of another CO, group but different orientation which is very unstable. All of these characteristics may facilitate the formation of higher density dolorna sinters.

Jan 1, 1995

By V. I. Lakshmanan

Crown ethers are gaining importance in separation technology specifically for rare earth elements (REE, La to Lu plus Y) and precious metals (Au, Ag, Pt, Pd, Rh and Ir) due to their specific binding ability, metal complex stability and high extraction efficiency. The selectivity of crown ethers in extraction of these metals depends on different factors, including the cavity diameter and nature of a donor atom of the crown ether, size and charge of the metal ion, diluents and counter ion. Demand for strategic REE and precious metals are consistently increasing in the world while the separation of these metals is most challenging tasks. In this paper, the use of crown ethers in separation of REE and precious metals, reaction mechanisms and simplified process flowsheets will be elucidated. New reagents with high selectivity for the separation of these metals are further expected to produce high purity metals.

By Z. B. Moukhametshina

The process of various zirconium alloys iodination by the iodine vapor was investigated. The nature of impurities, conditions of iodination, iodine flow rate, and zirconium tetraiodide condensation rate effect on the metal impurities transfer process was analyzed, both qualitative and quantitative correlations were established. Impurities were classified according their transfer extent. Another classification of impurities transport dependence on iodination process temperature was also offered. Obtained results were compared with impurities transport data in the process of iodide refining available in literature. Some impurities transport mechanisins and iodide-refined metals improvement possibility by means of iodination conditions control were discussed.

Jan 1, 1997

By John R. Goode

The fist part of this paper comprises a general discussion on refractory gold ores and their mineralogy. Processing methods now in use are reviewed and test procedures for the important methods are discussed. Factors determining the selection of a process are outlined. The paper includes a survey of production plants using pressure oxidation, roasting and biological oxidation to process refractory ore. The status of processes under development is briefly reviewed.

Jan 1, 1993

By T. Plikas, L. H. Gunnewiek, L. Oshinowo

"Electric furnace smelting is one of the principal unit operations for ferroalloy production, and increased process intensity, improved availability, minimal maintenance and a longer campaign life are common objectives for electric furnace operation in order to obtain favourable economics of production. Furnace designers have continued to develop innovative solutions, e.g., furnace cooling systems, that have allowed these objectives to be realised and CFD modelling plays a key role in the design process. Enhanced understanding of the energy transfer process in the furnace and the ability to develop, evaluate and optimize components of the crucible design to match process requirements are the key motivators for modelling.This paper provides an overview of recent applications of CFD to the design of electric furnaces. The aim is to illustrate what can be done, and identify areas where further work is needed in this field. Examples include furnace bath simulation, crucible cooling system design, taphole design, baking of Soderberg electrodes, off-gas systems, and fume control and building ventilation. It is argued that the trend is for numerical models to become more encompassing while at the same time more accessible, and therefore further improvements in furnace design will be realised with continued and well validated modelling efforts.IntroductionOne of the main processing steps in ferroalloy production is the smelting of ore in electric furnaces. The three-electrode, AC submerged arc furnace is most prevalent method for smelting in the industry, with shielded-arc and DC plasma arc furnaces achieving limited application (1,2). Commercial furnaces range in size from a few megawatts to more than eighty megawatts of supplied power, and operate with the objective of maximising the return on capital invested. Maximising productivity and energy efficiency are two pathways to achieving this objective, through process intensification, increased availability, minimal maintenance, and increased campaign life for the furnace and associated equipment. Concurrently, the need to reduce the environmental impact of metal production by controlling the emission of particulate emissions, greenhouse gases, and other harmful by-products must also be met."

Jan 1, 2004

By N. Kanari

The kinetics of oxychlorination of MgO by Cl2+O2 was studied in the temperature range of 850 °C - 1025 °C, using thermogravimetric analysis. The effects of C12/02 ratio, gas velocity, temperature and partial pressure of reactive gases on the reaction rate were investigated. The oxychlorination process was characterized by an apparent activation energy of about 214 kJ/mol. The reaction orders with respect to C12+O2. C12 and O2 at 950 °C were about 0.65.0.98, and -0.37, respectively. Some data about oxychlorination kinetics of MgO, Cr2O3, and MgCr2O4 contained in chromite were compared. Efficiency of using oxychlorination for the removal of iron oxides contained in magnesia was demonstrated.

Jan 1, 1999

By Salustio s. Guzman

The standard .free energies of formation of tin chlorides were estimated with reviewed and estimated basic thermodynamic data, and measured reversible potentials for the disproportionation of tin dichloride into metallic tin and tin tetrachloride. Values for cºp, Sº, Hº?-Hº 298, -(Gº - Hº298) /T,.Hºf, Gºf, and log Kp are given in tabular form, these estimations are compared with estimations reported in the literature.

Jan 1, 1985

By N. J. Themelis

In the last two decades, the Outokumpu flash smelting process has become the dominant new technology for copper smelting and has? also been applied to the smelting of other metal sulfides. The application of oxygen enrichment and improvements in concentrate burner and furnace design have resulted in ever increasing smelting rates per unit volume of the reaction shaft. This paper examines the. rate phenomena taking place in the reaction shaft of the Outokumpu furnace and compares information obtained from a mathematical model of heat and mass transfer rates to results obtained in pi1ot tests conducted at Pori, Finland, and to actual performance of a number of flash smelters around the world. 2?

Jan 1, 1985