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By David B. Dreisinger

Mass and heat balance modeling is a powerful tool for the design and analysis of hydrometallurgical process flowsheets. In this first of two papers, we examine the basic fundamentals of mass and heat balance modeling, and apply these concepts to several flowsheets using a simple spreadsheet model. In this way, we aim to demonstrate how such models are not only easy to construct, but can also be indispensable for comparing various flowsheet alternatives, for making rational economic decisions, and for developing a basic understanding of existing process behaviour.

Jan 1, 2002

By T. Shibasaki

Purification of copper electrolyte at Naoshima is carried out by two stage liberation to completely depress copper and impurity ions followed by concentration of the solution to produce crude nikel sulfate as by-product. A new nickel recovering process has been developed and pilot tested recently. It consists of the following process steps.; neutralization of spent electrolyte from liberation section to remove free acid and most part of remaining impurity ions, refining and nickel concentration by solvent extraction, and crystallization of pure nickel sulfate from concentrated strip solution. This paper describes the results of laboratory and pilot plant tests, then briefly discusses feasibility of the proposed process.

Jan 1, 1987

By C. Acuna

The standard procedure of fire refining consists of sulphur removal via air injected through tuyeres, arsenic slagging via soda-lime flux and oxygen reduction by air or oxygen deficient air or a steam fuel mixtures. The use of porous plugs to stir with an inert gas has been mainly considered as a surface renewing agent that increases the product quality and shorten the refining cycle. In the present study the effect of the bottom stirring by nitrogen gas injection through porous plugs for the treatment of the crude copper in the range of 400-150 ppm sulphur, 3,000?2,000 ppm arsenic and 14,000-7,000 ppm oxygen content was investigated. The combined effect stirring-reducing, by the use of air or a steam fuel mixtures through tuyeres for oxygen removal, follows a kinetics of first order where the constant, K, can be represented by the following polynomial expression: K = A .* R2 + B * R + C Where A, Band C are constants that depend on the nitrogen flow rate and R is the air-fuel ratio or the steam-fuel used in the reducing step. Depending on the optimization of the flow of nitrogen and the air-fuel or steam-fuel mixture and only if just the oxidation, complexing and reducing steps are considered, the process cycle might be shortened by 45%.

Jan 1, 2003

By Chuanhong Li, Zuohua Lin, Zhancheng Guo

"Catalytic mechanism of CeO2 in combustion of coals was investigated in this paper. Catalytic combustion of four kinds of coals with different metamorphic grades by CeO2 was examined, suggesting that catalytic function of CeO2 increases with increase of metamorphic grade of the coals. One important reason for CeO2 promoting combustion of the coals is that pyrolysis of anthracite is advanced by CeO2, which not only raises the pyrolysis rate and pyrolysis conversion ratio, but increases contents of light components in pyrolysis gas; and both pore space and specific surface area of the pyrolysis char are enlarged by CeO2, which is another reason. In order to realize in situ catalysis for reducing catalyst consumption, it is crucial to increase catalyst particle number and enhance the bonding force between catalyst and coal. In addition, remarkable energy saving effect was observed when a nanometer calcium-based rare earth catalyst obtained by hydro-thermal synthesis was applied to catalytic combustion of coal injection into blast furnace.Introduction Coal combustion is acknowledged as one of the most important coal applications. Since addition of catalysts could reduce the ignition temperature of pulverized coal and accelerate the coal combustion, catalytic combustion is generally accepted as an effective measure to realize fast combustion of coal. Furthermore, different catalysts added may produce different effects on ignition temperature of coal. It is reported activity of catalysts with the same cation follows this order: OH->CO3 2->Cl->SO4 2-; while that of the catalysts which have the same anion follows: Cs+>Rb+>K+>Na+>Ba2+>Li+>Sr2+>Ca2+>Mg2+>Be2+ [1-4] .Due to the special physical and chemical structure, CeO2 plays an important role in the catalysis field. Many literatures point out that CeO2 not only has great catalytic effect on energy conversion, succeeded in catalyzing combustion of gaseous fuels such as CH4, CO, etc. but also can catalyze combustion of some liquid and solid fuels such as JP-10, black carbon, carbon deposit in the automobile exhausts and so on [5-9].Pyrolysis, the first step of combustion, directly influences ignition temperature and combustion rate of coals. So a great variety of catalysts were applied to catalyze pyrolysis of coals. And plenty of studies suggest that the alkali and alkaline-earth metal compounds inherent in the coals show apparent catalytic effect on coal pyrolysis. Meanwhile, addition of alkali and alkaline-earth metals into coal combustion process also indicates obvious catalysis effect, accelerating coal pyrolysis, improving pyrolysis conversion ratio, increasing contents of pyrolysis gases and changing composition of the pyrolysis gases [10-15].Although alkali and alkaline-earth metal compounds have good catalysis effect on coal combustion, their application in the catalysis field was limited because of their erosive attack to the combustion equipments. In contrast, CeO2, as a substitution of the traditional coal catalysts, presents widely potential application due to its good catalysis ability, non-corrosive and nontoxic. However, investigation on CeO2 catalyzing coal combustion is rarely reported. In this work, catalytic mechanism of CeO2 in coal combustion was studied, in an attempt to provide theoretical foundation for developing new catalysis technologies."

Jan 1, 2009

By P. J. Uggowitzer, K. Steinhoff, A. Wolf

"With the increasing acceptance of the Thixoforging process in the last few years, also the technical and commercial requirements for this forming technology and its components increased. So far, a great deal of work has been done in the development of an efficient process and control design. However, less attention has been paid to the development of new specifically tailored aluminum wrought alloys for this specific manufacturing process. · In this paper a new AlMgSi-alloy (A6082), optimized for the Thixoforging process, is presented. In the first part, the technical potential of the new alloy is specified by its microstructural evolution and flow characteristics in the semi-solid state. In the second part, the mechanical properties of thixoforged components of different conventional AlMgSi-alloys a (e illustrated · and compared to the new alloy.IntroductionSemi-solid metalworking, also known as semi-solid forming, is a hybrid manufacturing method that incorporates elements of both casting and forging. The key to the process relies on the peculiar flow behavior of slurries containing non-dendritic solid, which was first studied at the MIT by Flemings et al. [i], in the early 1970s. It was discovered, that if an alloy is uniformly stirred during freezing, discrete rounded particles of solid are formed rather than the normal dendrites, and the slurry is highly fluid (-5 Pas) up at least 50% solid. In addition, these slurries posses thixotropic flow characteristics: the viscosity is dependent on sheare rate and time. The more vigorously they are stirred, the more fluid they become. However, on standing the viscosity recovers and the material stiffens (-106 Pas).The semi-solid forming process exploits this phenomenon. In a first step, the required non-dentritical- microstructure is obtained by mechanical or electromagnetic stirring during primary solidification of the alloy. The stirred slurry is generally fully solidified as a feedstock billet and - in a second process step - reheated above the solidus temperature into the semi-solid state. In this condition, the thixotropic properties permit the material to be handled by robotic devices and transferred to a die (Thixocasting) or subjected to- a forming process by means of forging (Thixoforging). Owing to the shear stress which acts on the semisolid material during forming operation, the viscosity of the material is reduced attaining so the desired fluid-like flow characteristics."

Jan 1, 2000

By Binxu Zhaug, Mark Jolly, Xiaojun Dai

"In conventional investment casting process of aluminium alloys for the application of the aerospace industry, to assure the quality of the final casting, usually the foundry uses large runner system which results in low yield, high energy consumption and high GHGs emission. In one case of this investigation, the yield is between 5 ~ 10% which means that the current casting process wastes large amount of energy and generates lots of scraps. By applying a new casting method, the bulky runner system and the melting/holding time are significantly reduced, the quality of the casting is improved, and in the meantime the related energy consumption and GHGs emission are significantly decreased. In the investigation, the energy efficiencies and GHGs emission between the current and traditional processes are calculated and compared.1. IntroductionAs one of the conventional casting process, Investment Casting Process (ICP) and its applications can be traced to thousand years ago [l]. In current casting industry, ICP still plays an important role in the production of small and precious castings with high quality requirements in automobile and aerospace industries. Both casting quality and manufacturing costs which mainly consist of energy costs have crucial effects on the competitiveness of castings in the market. In the production of aluminium alloy castings using ICP, the energy cost and energy efficiency of a casting facility depend mainly on the efficiency of its melting and heat treating performance. In association with the two performances, more than 60 % of the total process energy costs are symbolised in a typical casting facility [2]. Additionally, in conventional ICP of aluminium alloys for the application of the aerospace, to assure the quality of the final casting, typically the foundry uses huge runner system including big risers/feeders which cause low yield, creates lots of scraps and generates high energy consumption. Consequently, there are huge opportunities for casting industry to choose the best practices for potential energy saving. Furthermore, the reasons such as the stringent limitation of environmental legislation in Europe and the pressure of the rising energy price force the casting industry to reduce the energy consumption and greenhouse gases (GHGs) em1ss10n."

Jan 1, 2012

By Lv Guozhi, Niu Liping, Shi Guanyong, Liu Yan, He Jicheng, Du Yanjun, Dou Zhihe

"We proposed thermit reduction-electroslag remelting method of preparing the large scale CuCr alloy. But there are pores and oxide inclusions in CuCr alloy prepared by thermit reduction process. This paper studied mainly the effects of ratio of reactant and additive on the inclusion type and their occurrences in CuCr alloy. The alloy prepared in different process conditions was characterized via XRD, SEM, OM and TEM and metallographic microscope, in which the existing state and micro-structural defects of inclusions are analyzed. The results show that there are three distinct regions: copper-rich regions, chromium-rich regions and the inclusion regions. Inclusions are mainly in the form of stomata and Alz03 phase, mainly locating in the copper-rich phase and the interface area of chromium-rich phase and the copper-rich phase. Adding Na3AlF6 and heating agent can effectively reduce the inclusion content in the alloy.1 IntroductionIn recent years, with the development ofhigh power vacuum and high-pressure technology ,the CuCr alloy contact material which has many advantages gradually replaced the traditional W-Cu and Cu-Bi series alloy contact material, and become the first choice of material in high-voltage and high-power vacuum switch contacts['-3l. The traditional powder metallurgy method, infiltration method and vacuum arc melting method[4-SJ are using metal Cu powder and Cr powder as raw material by casting molding, and have disadvantages such as high production costs, complicated process, poor product density and low yield, especially in the large size alloy ingots[9-12l. At present, the world regards CuCr alloy new preparation technologies as the first place, and how to achieve a large size the CuCr alloy ingot preparation has become a hot research of CuCr alloy[3l. Zhang Ting-an and Dou Zhihe[l-3l who are supported by national natural science fundation of china successfully successful developed new technologies and core equipment to prepare large-size copper-chromium alloy through aluminum thermal reduction-secondary refining method, and obtained two national invention patents. The method includes two key steps: one is get CuCr alloy consumable ingot by Thermit-SHS with electromagnetic stirring, the other is to refme the CuCr alloy ingot to remove the pores, inclusions and other defects by electroslag remelting technology to get dense and uniform CuCr contact material. The preliminary study results show that means of electromagnetic stirring evidently inhibit effect of alloy ingot macrosegregation during the electromagnetic casting stage, but there are still microstructure defects such as alumina inclusions and pores in the alloy ingots. Therefore, Zhang Ting-an et al refer new ideas of using the electroslag remelting to refine Cu Cr alloy ingots and effectively remove the defects of the ingots such as pores and inclusions [3l _ At present, there is no report of study on the electroslag remelting refining processes of CuCr alloy (the refining slag, remelting current). This article will research mode of occurrence and distribution law of inclusions in the large-size CuCr alloy ingots by Al Thermit-SHS under magnetic field stirring action and provide a theoretical basis for chosing refining slag to remove inclusions by electroslag refining. Meanwhile the article analyses the effect of reduction conditions of Thermit-SHS on the types of inclusions, mode of occurrence and distribution of regular inclusions in alloy ingot, and refer theory for inclusions regulation in the large-size alloy ingots."

Jan 1, 2013

The standard procedure of fire refining consists of sulphur removal via air injected through tuyeres, arsenic slagging via soda-lime flux and oxygen reduction by air or oxygen deficient air or a steam fuel mixtures. The use of porous plugs to stir with an inert gas has been mainly considered as a surface renewing agent that increases the product quality and shorten the refining cycle. In the present study the effect of the bottom stirring by nitrogen gas injection through porous plugs for the treatment of the crude copper in the range of 400-150 ppm sulphur, 3,000-2,000 ppm arsenic and 14,000-7,000 ppm oxygen content was investigated. The combined effect stirring-reducing, by the use of air or a steam fuel mixtures through tuyeres for oxygen removal, follows a kinetics of first order where the constant, K, can be represented by the following polynomial expression: K = A * R2 + B * R + C Where A, Band C are constants that depend on the nitrogen flow rate and R is the air-fuel ratio or the steam-fuel used in the reducing step. Depending on the optimization of the flow of nitrogen and the air-fuel or steam-fuel mixture and only if just the oxidation, complexing and reducing steps are considered, the process cycle might be shortened by 45%.

Jan 1, 2003

By I. D. Reznik

Results of thermodynamic computations have been presented for reactions occurring in the process of segregation roasting of oxide nickel ores to describe more accurately the mechanism of the process. Under conditions of laboratory-scale roasting in combination with close-circuit flotation flow-sheets and magnetic separation, a recovery of 80-82% of nickel into 8 to 10% Ni concentrate and a recovery of up to 66% of cobalt was achieved. Process conditions have been selected for processing of both high-iron and high-magnesium ores. The feasibility of conversion of 94-98% of nickel and cobalt into solution by oxidizing pressure leaching with sulfuric acid has been demonstrated. It has been substantiated that it is reasonable to introduce double-stage segregation roasting.

Jan 1, 2003

By R. Hurman Eric

The electrode in a slag-resistance electric furnace is the central factor in the design and operation of the furnace by its role of conveying the smelting power, i.e. heat needed for the operation. The control parameters are the size and positioning in the slag bath which are defined by slag resistivity, furnace resistance, cell constant and power input sequence all of which are closely interrelated. The flow of heat generated by the electrode current determines the energy distributions and thus the furnace dimensions. Heat flow models concerning vertical, horizontal and combined two-dimensional flows are discussed. All these considerations are based on the experimentally determined slag properties such as its resistivity.

Jan 1, 1995

By A. V. Tarasov

The proposed process is based on creating a controlled frothed layer of molten slag, in which fine particles of carbonaceous reductant and raw material to be processed are mixed with emulsified iron. Frothing of the slag layer without external blowing occurs as a result of intensive evolution of gaseous reduction products. The froth reaction process is maintained due to the heat of an electric arc in the slag layer. When the metal bath is heated by the arc to 1400- 1 500°C, the low temperature of the slag surface of about 1200-1 300°C is maintained due to low thermal conductivity of slag froth preventing heat loss. In order to maintain the required slag froth level and control the process temperature, air tuyeres are installed above the slag bath; blowing air serves also for oxidation of zinc in fumes and for its transportation. High adsorption and thermal insulating properties of slag froth ensure virtually complete elimination of dust and mist entrainment along with low heat losses. The main macrokinetic regularities of the carbon thermal reduction of zinc-containing slag melts have been studied under frothing conditions. The mechanism of formation of gas-slag emulsion has been identified under the conditions of reaction [C]+[O]=CO occurring locally at the slag-metal interface. It has been demonstrated that under the froth reduction conditions the zinc removal rate from the melt increases on the average by 3 to 5 times. Based on the physical and chemical data obtained, basic principles of the dezincing technology have been developed for different intermediate oxide iron-containing products produced in the process of ferrous and non-ferrous metals production.

Jan 1, 2002

By B. Q. Li

A numerical study of the developing fluid flow and thermal aspects during the staning phase of aluminum continuous casting processes is presented. The deforming finite element method, coupled with a quasi-Lagrangian formulation, is used to represent the growth of an ingot and the dynamic fluid flow and thermal behavior that evolves in the growing ingot. The mathematical formulation of the problem and the numerical treatment are discussed. The algorithm solves the free moving nodes as part of total unknowns with an automatic time step control for time integration. This permits an optimal computing efficiency while still keeping the computational errors under control. A selection of the results obtained using the algorithm is presented. The results are concerned with the evolution of fluid flow, temperature and solidification phenomena during a DC round ingot casting process, as it evolves from the beginning of casting operation to a steady state. These results show that the time-varying, complex fluid flow and thermal phenomena during continuous casting processes can be very well represented by the computational algorithm. The results also illustrate that, during the casting process, ~e fluid flow and temperature fields change drastically at the initial stage but evolve slowly afterwards

Jan 1, 1993

By Hong Ouyang

A unified computational model has been developed for the Bridgman growth processes of B-NiAI and CdTe crystals. To handle the geometrical and physical complexities, a two-level approach has been developed. At the gtobatlevel, conjugate heat transfer, phase change dynamics, and variable material properties along with the realistic geometries and thermal boundary conditions are accounted for inside the entire crystal growth system. Refined calculations are then made within the ampoule, with the boundary conditions supplied by the global simulations. This model can optimize the use of computational source, help understand solidification behaviors, and improve designs of crystal growth system.

Jan 1, 1996

By Fathi Habashi

During the recovery of copper, nickel, zinc, and lead from their sulfide ores, large amounts of sulfur dioxide are generated. A fraction of this gas is captured and transformed into sulfuric acid and liquid SOl and the remainder is emitted to the atmosphere. Numerous proposals were made to solve this problem. Hydrometallurgy offers the only valid solution by which elemental sulfur instead of sulfur dioxide can be produced. Sulfur can be easily stored, transported long distances, or transformed into S02 and H2S04 when desired.

Jan 1, 1996

By Eric J. Grimsey

Nickel smelting and converting can be viewed as processes in which iron is either partitioned or transported between matte and slag. Metal recovery depends on the mass of iron transported to slag, the thermodynamic environment in which the transport is made, and the extent to which the slag, once formed, is left in contact with the matte. The importance of these effects is discussed with reference to a new equation which describes metal recovery in terms of a mass balance and a thermodynamically related parameter which is easily measured in practice.

Jan 1, 1993

Mount Isa Mines Limited (MIM) and the Commonwealth Scientific and Industrial Research Organization (CSIRO) have, over the past 15 years, jointly developed the Isasmelt process. This process is based on the use of the Sirosmelt top-entry, submerged combustion lance, developed by the CSIRO in 1973. While the Isasmelt technology was first applied to lead smelting, it has more recently been adapted to smelt copper concentrate. A 15 t/h demonstration Copper Isasmelt plant was commissioned in MIM's Mount Isa copper smelter in April 1987. The success of the Copper Isasmelt demonstration plant, which smelted over 532,000 metric tons of copper concentrate, has led to the construction of two full-scale furnaces: a 104 t/h furnace in the Mount Isa copper smelter, and a 585,000 t/y (650,000 short t/y) furnace at the Cyprus Miami Mining Corporation smelter at Miami, Arizona. The commissioning of these furnaces commenced in August and June 1992, respectively. The MIM Copper Isasmelt furnace will raise the Mount Isa copper smelter's capacity to 265,000 t/y of copper. The plant includes several innovative features, including: Andritz pressure filters, a rotary holding furnace, and an Ahlstrom flux-flow boiler.

Jan 1, 1993

By Juan Patricio Ibáñez

Separation of arsenic and copper from Cu-As-H2S04 electrolytes by electrodialysis has been investigated at room temperature. The effects of current density and pH were studied. An arsenic-free copper solution was obtained for all the tested conditions. The transport efficiency for copper ions was found to be higher than 98% after 3 hours' test. Transport of arsenic and copper through the ion exchange membranes was increased by increasing pH and current density. Solution pH was found to be a key parameter for the separation process, since it controls the speciation of the ions to be transported and the formation of unwanted precipitates which reduce the global efficiency of the electrodialysis process. The main conclusion is that electrodialysis is a promising technique to be used in separating and/or concentrating ions of interest in copper electrometallurgy.

Jan 1, 2003

By Tianming Sun, Gabriella Tranell, Ragnhild E. Aune, Mark William Kennedy

Rare Earth Elements (REEs) are critical for the production of many advanced materials and products. Mining and primary production of REEs are generally associated with significant environmental impacts. By recovery of REEs from secondary sources, through recycling or as a byproduct, the adverse environmental impacts may be partly avoided. In the present study apatite concentrate originating from iron ore beneficiation done by LKAB in Kiruna, Sweden, is explored as a possible source for REEs. The composition and distribution of the REEs within the concentrates are studied using ICP-MS, XRD and SEM-EDS/EPMA, as well as the melting point and heat of fusion using DTA-TGA-MS. The behavior of the material during melting has also been studied through wetting and slag saturation experiments. The overall aim of the study is to evaluate the implications for future smelting experiments aimed at concentration and recovery of the REEs.

Jan 1, 2015

By George Owusu

A study has been carried out on the use of solvent extraction, instead of the traditional zinc dust cementation process, to remove copper from concentrated zinc sulphate leach solutions. In a series of experiments using plant solution containing 1.9 g/L Cu, 2 g/L Fe, 173 g/L Zn, 7.9 g/L H,SO,, 0.25 g/L Cd, 15 mg/L Co etc. and LIX 622 in SX-1, up to about 97-98 % of copper present in the zinc sulphate leach solution was extracted with negligible co-extractions of zinc, iron, cadmium, cobalt, etc. pH modification was not required for this reagent. The copper loaded organic was almost completely stripped using 150 g/L sulphuric acid. Investigations into the effect of any possible organiclextractant contamination on zinc electrowinning showed (if any) little effect on current efficiency if the organic contamination is less than 45 ppm; current efficiencies of 95-97 % were obtained. At organic contaminations higher than 45 ppm, the current efficiency dropped to about 92- 94 %. Visually, the organic-contaminated cathode sheets had rough surface morphology, becoming more intense with increasing organic concentration, compared to the non-contaminated cathode sheets.

Jan 1, 1998

By Olusegun J. Ilegbusi

"A two-fluid model is used to calculate flow and heat transfer characteristics of a plasma jet. This model accounts for both gradient-diffusion mixing and unmixing that may result from pressure-gradient-body-force imbalance in the system. The unmixedness is considered to be essentially a Rayleigh-Taylor kind instability. Separate transport equations are solved for the plasma and ambient gas velocities, temperatures and volume fractions. The two fluids allowed to exchange mass, momentum and energy through empirical interaction parameters. The empirical coefficients are first established by comparison of predictions with available experimental data for shear flows. The model is then applied to an Argon plasma jet ejecting into stagnant air. The predicted results show the significant build-up of unmixed air within the plasma gas, even relatively far downstream of the plasma torch. By adjusting the inlet condition, the model adequately reproduces the available experimental data on the temperature profile.IntroductionPlasma jets have important applications in materials processing, some of which include spray deposition, melting and refining, heat treatment and materials synthesis. In a typical reactor, the hot plasma stream entrains a surrounding gas and the resulting heat and mass transfer and the condition of operation of the torch, determines to a large extent, the performance of the unit. The entrainment may prevent uniform mixing and produce regions of unmixed hot/cold gases and non-uniform deposits as a result of insufficient melting of deposit in cold regions. This phenomenon may also affect chemical reaction rate in plasma systems for NOx reduction in exhaust gases.The study of plasma phenomena is often conveniently divided into three parts namely, the plasma torch, the plasma jet and analysis of the particles carried in the jet. The present work concerns processes occuring in the near-field of the plasma jet i.e. just downstream of the torch."

Jan 1, 1994