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By F. Patisson

During exothermic gas-solid reactions, heat generation makes temperature rise and modifies the rate of the various mass transfer processes, namely the chemical reaction itself, the pore diffusion and the external transfer. We have investigated this thermal effect during the oxidation of zinc sulfide porous pellets in a thermo balance furnace, between 550 and 900°C-and under O2-N2 atmosphere. The results have been' analyzed by using, firstly, the law of additive reaction times derived from the isothermal Grainy Pellet Model, and, secondly, a new numerical model taking into account non-isothermal conditions. Both the models can satisfactorily simulate conversion versus time, but the numerical model also depicts the temperature evolution within the pellet. Finally it is shown that owing to the heat generation the zinc sulfide oxidation takes place under diffusion control (3/4 internal, 114 external) in all the cases studied. During the course of reaction, the. pellet undergoes strong temperature variations, with thermal gradients confined to a shell oxide layer.

Jan 1, 1996

By John J. J. Chen, Barry J. Welch

"As in many industrial processes, the detailed mechanisms involved must first be understood before being able to redesign, or to carry out improvements or optimisation of the process and equipment performance. In a great majority of metallurgical processes, visual observation and actual measurement of process variables are either very difficult or near impossible. Often, the cost and effort involved are prohibitive. Consequently, physical modelling is often used to provide some understanding of the process and for the validation of computer numerical models. In this paper, we summarise some of the work carried out at The University of Auckland on the modelling of the Hall-Héroult electrolytic cell, the in-line melt treatment process, and the steel casting tundish. IntroductionIn any industrial process, it is essential to understand the underlying mechanisms before any optimization or process improvement can be carried out. In many metallurgical operations, the processes are conducted at elevated temperature and under rather hostile environments. Consequently, it is often difficult, and sometimes impossible, to observe the actual processes occurring, or conduct measurements which are pertinent. In some situations, it is possible to formulate mathematical equations purported to describe the process, and obtain the solutions numerically. However, in this latter case, the validity of the simplifying assumptions made are often uncertain. Physical modelling may provide the necessary information for the validation of such numerical models. Furthermore, through an application of the principle of similitude, it is possible to apply data obtained from physical modelling to actual metallurgical processes. This paper will summarise some the work carried out at The University of Auckland on the physical modelling of gas-induced flow in the Hall-Héroult electrolytic cell, an in-line melt treatment unit, and the flow in a steel casting tundish.Gas-Induced Flows in a Hall-Héroult CellIn an aluminium cell, the effects due to electro-magnetic forces have been addressed and various design modifications such as magnetic shielding and the positioning of risers have been carried out to control or lninimise the effects of magnetic fields'. Consequently, the effects of gas-induced flows are now becoming significant providing the impetus for the study of the gas behaviour in the bath. Furthermore, the shape and size, and the rate of evacuation of the anodically generated gases affect the cell voltage affecting the energy efficiency; at the same time, the back-reaction between the anode gas and the metal produced is the predominant cause of the loss of current efficiency. Figure 1 shows a cross-section of a conventional cell in which the gas evolution occurs directly under the anodes, and the gas induced flow is confined mainly to the region occupied by the bath"

Jan 1, 1994

By E. Oshima

The only one reverberatory furnace smelting in Japan has been alive in Onahama Smelter, Onahama Smelting and Refining Company. The fuel for the reverberatory furnaces had been changed from bunker C-oil to mainly coal and partially waste tires to reduce the energy cost. The steam, recovered by the waste heat boilers of the reverberatory furnaces, has been utilized fully for the power generation to save the purchase power. Copper concentrate has been smelted also by injection through tuyeres in the P.S. converters since 1983. The amount of concentrate, treated in the converters, was increased by the construction of small oxygen plant in December, 1990. In the paper, the current practice and improvements in the reverberatory and converter operations are described.

Jan 1, 1993

By John R. Howell

"SUMMARYThe process of producing a new cast component requires significant design and development by both the design engineer and the foundry engineer. This effort strives to produce a high quality component at minimum cost. To assist in this development, an analysis system, consisting of several computer programs, has been developed to simulate the metal casting process. This system incorporates analytical geometric solid modeling, finite element analysis, results display, and an innovative technique to model the casting mold with surface boundary conditions.The simulation has produced excellent thermal results and work is in progress to develop techniques to enable use of this data in additional analyses to predict porosity and residual stress. Research is required to produce working parametric formulations of material properties. Software development is required to develop good fluid flow analyses for large. 3D models to simulate filling of and convection in molds.Integrating this system of programs is difficult due to proprietary database structures used by software developers. However, an acceptable means has been accomplished' to move data from one program to another. Further software development is required to facilitate this task. INTRODUCTIONThe process of producing a new cast component requires significant design and development by both the design and foundry engineer. This effort strives to produce a high quality, reliable component at minimum cost in a timely manner. The design engineer needs to know the physical and mechanical properites which can be expected in the actual part at critical areas. This will enable him to design a part with minimum material while fulfilling the performance required. The foundry engineer needs to produce a sound, quality casting with a minimal amount of material In risers, the feeding system and machining stock. This must be done with a minimum· investment in tooling and development time and maximum productivity of labor and capital employed. This task Is continually being made more difficult because of increased competition in the marketplace and the use of castings in more severe service. This has strongly influenced the need for high quality castings.The task of developing a new casting is difficult for both the design and foundry engineer. To assist in this development, Deere & Company has been engaged in the development of an analysis system to simulate material processes. A major portion of this program involves simulation of the metal casting process. This analysis system has evolved into a package of computer programs which simulates casting solidification and subsequent cooling through the finite element method"

Jan 1, 1986

By Thomas P. Battle

Ilmenite (iron titanate) is the source of over 90% of all the titanium produced in the world today. At some point during production of titanium dioxide or titanium metal the iron impurity must be removed. Too often it becomes a waste instead of a product. DuPont and MINPRO have developed a solid-state process which separates the iron and titanium components of ilmenite into different high-purity powders, which can be separated using conventional mineral processing techniques. The main reactor in this process is a unique high-temperature ball mill, where the iron segregates from the ilmenite lattice with the assistance of catalytic quantities of He\. The results of lab, pilot plant, theoretical, and scale-up studies are presented and discussed.

Jan 1, 1996

Al2O3,-WC Composite powder for cutting tools was synthesized by self-propagating high-temperature synthesis using A1 powder as a reducing agent. WC, W2C and Al2O3 were concurrently formed in WO3Al-C system. It was found that the complete reaction was achieved with excessive addition of carbon and appropriate processing parameters such as degree of dilution, particle size of aluminum, compaction pressures of green pellets and carbon source. The final product which was leached by 50% HN03+HF diluted solution was consisted of Al2O3-55wt% WC having 2-3um of mean particle size.

Jan 1, 1999

By Mingming Zhang, Marshall S. Coe, Marcelo W. Andrade

To supply iron units and flux burden in blast furnaces, sinter basicity is one of the vital parameters for sinter plants. The sinter basicity also plays an important role in sinter quality since it imparts the formation of different mineral phases in sinter. Pot-grate sintering tests were carried out with low and high basicity to investigate the effects of sinter basicity on sinter mineralogy, properties and productivity. It was found that with an increase in sinter basicity, both sinter productivity and reducibility (RI) increased. Tumbler index (TI) and low temperature degradation index (LTD) of high basicity sinter were comparable to low basicity sinter. Softening and melting tests showed that sinter with 3.5 C/S basicity had slightly higher softening temperature comparing to lower basicity sinter with C/S 2.6, acid and fluxed pellets. XRD analyses confirmed the formation of silico-ferrite of calcium and alumina (SFCA) and calcium ferrite (CF) in the tested sinter samples.

Jan 1, 2015

By D. G. Mason

During the design of copper refinery tankhouses, there is a need to develop mass balance calculations for many process components, so that optimum physical plant configuration is achieved. Each mass balance is complex, possibly with over 120 interactive variables as basic input data. Recent developments in tankhouse design (e.g. permanent cathodes) have greatly increased the design options available for any project, multiplying even further the requirement for calculations. In the past these calculations were tedious and susceptible to human error. A comprehensive computer program can now simplify the task of the process metallurgist, enabling more sophisticated and sensitive plant designs to be produced. The paper describes the successful development of a flexible mass balance program that originallly was used in a feasibility study which had to be completed within a short time schedule. The program has been further developed and used for design and energy calculations; it can be usefully applied to existing plants to assess the impact of variations in operating parameters. The software takes account of staged liberation, electrolyte purification bleed and generates a reliable process inventory listing: it can also cope with stripper starting sheet options and disparate commercial circuits.

Jan 1, 1987

By J. H. Corrigan

A series of six papers describing the Falconbridge Dominicana Ferronickel project were presented at the International Laterite Symposium held as a joint project of TMS-AIME in February 1979 at New Orleans. A review of the ore mineralogy, as well as. the processing and environmental practices as they exist today at Falcondo with emphasis on modifications put into practice since 1979 are presented in two papers: Part I.- Mineralogy and Ore Dressing E.W. Lithgow - General Superintendent ? Mines Falconbridge Dominicana, C. por A. Bonao, Dominican Republic Commercial volumes of nickeliferous laterite ores overlie part of a 90 km long belt of peridotites in central Dominican Republic. Protores are serpentinized harzburgites and dunites, with lesser serpentinite. The ore mineralogy consists mostly of goethite, serpentine-group minerals, quartz and poorly crystallized, X- ray amorphous materials. Minor constituents are hematite, gibsite, olivine and enstatite. In the Ore Dressing plant, the mine feed is subjected initially to proper sizing and blending to produce a homogenized mix. Subsequent drying and upgrading, by selective crushing and screening of rock kagments through a Barmac circuit, complete preparation of the ore for pyrometallurgical processing. Part II.- Pyrometallurgy, Fuel and Power Generation J.H. Comgan - Manager ? Production Falconbridge Dominicana, C. por A. Bonao, Dominican Republic Falcondo's energy requirements are based on oil which is refined on site to provide distillate to carry out drying and selective reduction of the nickeliferous ore in the shaft furnaces, plus bunker oil to produce electrical power for process melting, refining and ancillary use. The dryer product at 1.68% Ni is briquetted and passed counter current to hot reducing gas in 12 vertical shaft furnaces. The hot calcine discharge is melted in two high power electric furnaces at very high secondary voltage. The crude ferronickel is ladle refined and cast as 15 kg ingots or 125 gm ferrocones.

Jan 1, 1993

By Wenxian Zhu, Patrick R. Taylor

"The small dimensions of nano-sized materials leads to novel and enhanced mechanical and physical properties. A thermal plasma reactor has been developed to study the formation of nanometer sized metal powders. A supersonic nozzle and a powder filter were designed and built. By vaporizing coarse metal powders in the plasma flame, and quenching the metal vapors through the nozzle at the rate of 107 K/sec, nanometric sized powders have been produced. The powders were collected in an airtight secondary quench-filter system. The particle size of the product power is 5 -20 nanometers, obtained through TEM analysis. The XRD analysis showed that the powder did not oxidize after the filter was handled in an inert atmosphere glove box.IntroductionNanostructured materials have been shown to exhibit improved physical and mechanical properties compared to conventional materials with larger grain sizes (1,2). There have been several methods proposed for preparing nanometer size materials. Thermally induced vapor-phase reactions have been used to produce a variety of powders. A common feature of these processes is the rapid production and cooling of condensable reaction intermediates and products, by gas-phase reactions, leading to the formation of a large number of very small particles. Thermal plasma synthesis of ultra-fine size particles has been attracting increasing interest (3,4,9-11), because it offers many advantages, especially in refractory materials processing, compared to conventional processes: (a) thermal plasma temperatures are very high(> 5000 K); (b) the rates of chemical reaction are much faster than those encountered in conventional processes; (c) high-purity materials may be obtained using fewer processing steps by collecting the product at temperatures where the by-products are in the vapor phase; ( d) the mean particle diameter can be controlled; (e) unifom sized particles may be produced with clean surfaces (these particles are particularly suitable for pressureless sintering); and, (f) high throughput per reactor volume can be achieved. In addition, the process used for generating particles determines the degree of sintering ability of the powders, since the process dictates the morphologies, the purity and its size distribution. In the future, thermal plasma synthesis nanometer size particles may play an important role in vapor phase reaction techniques and might be expected to be one of the first full scale commercial installations in the future."

Jan 1, 1998

By Dan Wang, Yuanbo Zhang, Guihong Han, Guanghui Li, Tao Jiang, Yanfang Huang

"Hematite concentrates are characterized by bad high-temperature reactivity and poor balling index, which restrict their large-scale application in the production of oxidized pellets. An organic additive, namely MHA, was authorized and used as binder recently in China. Compared with bentonite, the effects of MHA on compressive strength of hematite pellets at various firing conditions were investigated in this study. Experimental results showed the compressive strengths of preheated pellets with different binders were increased with increasing the preheating temperature and time. The compressive strength of preheated pellets with MHA binder was lower than that of pellets with bentonite, which can be ascribed to the high porosity of pellets with MHA binder. However, the compressive strength of roasted pellets with MHA binder was higher than that of pellets with bentonite. The compressive strength of finished pellets balled with MHA binder 1.0 wt% could meet the operation requirements of grate-kiln process.IntroductionHematite concentrates are characterized by bad high-temperature reactivity and poor balling index, which can lead to the appearance of those problems with increasing the energy consumption, shortening the useful life of equipment, and finally increasing the operation cost of oxidized pellets plants [1-2]. Some investigations have been conducted based on improving the pelletizing technique of hematite concentrates, such as pretreatment of raw materials [3-7], optimization of ore proportioning [8], addition of solid fuels [9-16], and so on. Employing high pressure grinding roller for the treatment of hematite concentrates revealed that the mechanical strength of wet green pellets could be improved. However, the mechanical strength of fired pellets was not improved obviously [7]. Huang, et al., pointed out that the preheating and roasting temperature may be decreased and the compressive strength of fired pellets could be increased by blending a certain proportion of magnetite concentrates with hematite [8]. Nevertheless, there are a variety of magnetite ores different in physical and chemical properties in China, resulting in the instability operation [17]."

Jan 1, 2012

By A. P. Pavia

Investigation on profitable ways to recover significant quantities of silver remaining dissolved in highly concentrated chloride solutions frequently pass through the development of solvent extraction (SX) routes. In this work, the general pathways involving Ag(I) extraction by dibutylthiourea (DBT) or tetraethylthiuram disulfide (disulfiram, DSF), from concentrated acidic chloride solutions, are investigated. With this purpose, the dependence of Ag(I) distribution coefficient on ligand and chloride concentrations has been analysed. Furthermore, in order to check whether there is some protonation at any site of DBT or DSF after contact with adequate chloride phases, lH NMR has also been used. The collected spectroscopic data suggest that anionic Ag(I) extraction reactions are not likely to occur. Based on the overall results achieved, proposals for the most probable Ag(I) extraction reactions are made.

Jan 1, 2001

By J. -S. Park, H. -S. Jeon

This study has been carried out to develop a relatively simple hydrometallurgical process for recovering nickel as nickel sulfate from the spent nickel-cadmium battery residue in which cadmium was removed by vacuum distillation. This residue is composed of 36 % nickel, 20 % iron, and other metals such as cobalt. First, crushing and selective classification were performed to separate iron to produce a nickel-rich product (over 40 % nickel). This product was dissolved in sulfuric acid to obtain a nickel sulfate solution. During the dissolution, nitric acid and air were added to the system to enhance the iron oxidation reaction rate. The free acid remaining in the dissolved solution was neutralized by adding nickel carbonate. Iron was precipitated as iron hydroxide and removed from the solution. The nickel sulfate solution was then fed to a vacuum evaporator to concentrate the solution by evaporation of water and crystallized at around 45°C to obtain nickel sulfate hexahydrate. A recrystallization process could remove other impurities such as zinc and manganese.

Jan 1, 2000

By Sergio N. Monteiro

Fibers extracted from the ramie plant have been traditionally used in textile and are now being considered as polymeric composite reinforcement owing to their superior strength. Recently the mechanical behavior of ramie fiber reinforced polyester composites was investigated but no significant improvement was found. Therefore, the objective of this work was to carry out a similar investigation by changing the type of polymeric matrix. Specimens with up to 30% in volume of ramie fibers incorporated into epoxy were bend-tested until fracture. The results showed a moderate improvement with a tendency of decreasing stress for higher amounts of ramie fibers due to the weak interface developed with the epoxy matrix.

Jan 1, 2009

By Mahesh C. Meyer Jha

AMAX has developed a chloride refining process to produce pure nickel and cobalt metals from mixed sulfide .precipitates, Metal chloride solutions, generated in a hydrochloric acid leaching step and purified in a solvent extraction circuit, are converted to metal oxides .and HCI gas by pyrohydrolysis. A pilot plant consisting of a 30-inch diameter fluidized bed reactor and other ancillary units was designed, constructed, and operated for over one year. Process design was aimed at minimizing energy consumption, maximizing conversion efficiency, and achieving simplicity of operation and control. The operation provided valuable information on process scale up parameters, process control strategies, and materials of construction., Several process variables such as bed temperature, solution composition, solution feeding system, bed particle size distribution, and fines recycle system were investigated to determine their effects on process efficiency and the physical and chemical characteristics of the product.

Jan 1, 1985

By J. B. Cocanour

Pioneering work at the U.S. Bureau of Mines (USBM) has produced a personal computer (PC)-based, software-driven video photometric color sensor for real time process control of metallurgical streams. The video photometer is an inexpensive optical sensor which operates in the visual area of the electromagnetic spectrum and collects color information through plastic optical fiber. The red, green, and blue (R/G/B) voltage components of the color video signal are digitized and characterized through software and then presented as the control variable for software-based proportional-integral-differential (PID) control. This sensor has been successfully employed in the control of a laboratory copper electrolytic circuit. With this sensor, copper solutions were analyzed on-line without the need for sample removal, dilution, mixing or reagent addition, thereby allowing for the real time control of the circuit.

Jan 1, 1994

By A. Tsubouchi, F. Noguchi, T. Takasu

"A high current density operation is desired to improve the productivity in copper electrorefining. However, a lot of problems still remain such as passivation at anode, dendritic deposition at cathode and impurity behavior during the electro refining.Effects of the current densitY on the morphology of copper deposition on the cathode, and passivation at the anode were investigated at various fluid velocity of electrolyte in the present study.Although a granular appearance of the copper deposition was obtained with increasing high current density, it was depressed by an increase of the fluid velocity of the electrolyte. A uniform deposition on the cathode was also observed when the fluid velocity of the electrolyte become higher. It was ascertained that passivation at the anode was suppressed by circulating electrolyte during electrolysis. INTRODUCTIONIt is desirable to operate at high current density in copper electrorefining in order to improve plant productivity without enlarging the size of electrodes(1). However, there are many problems in copper electrorefining at high current density with the usual commercial practice, for example, anode passivation, dendritic deposition and an increase of impurities in the cathode.In general, it is effective to agitate the electrolyte in order to suppress these problems(2). Smith et a1.(3) have performed electro refining experiments at various current densities in the range of 8 to 32 Aldm2 and at electrolyte fluid velocities in the range of 40 to 120 mlmin, and they obtained well consolidated, void free copper even at high current density in a high electrolyte velocity. However, they did not discuss the recovery ratio and the passivation behaviour at the anode. Walsh et a1.(4)(5)(6) experimented with the rotating cylinder electrode, and ascertained that electrolysis can be carried out at high current densities under the condition of pure electrolyte.With regards to anode passivation, there are several papers by previous workers(7)(8). Our group ascertained the process of producing anode slime during electrolysis(9). However, these experiments were carried out without forced circulation of electrolyte. Therefore, in the present study, to solve these problems, we electrolyzed at current densities in the range of 4 to 50 Aldm2 with circulating electrolyte in the range of 0 to 48 mlrnin. The effect of electrolyte fluid velocity on the surface morphology of deposited copper at cathode and passivation at anode were investigated when electrolysis were carried out with circulating electrolyte at high fluid velocity and at high current density."

Jan 1, 1997

By James R. Craig

Petroleum coke is becoming an increasingly important source of light hydrocarbon products as product crudes become heavier and of poorer quality. The use of petroleum coke to generate synthesis gas results in the formation of residual slags that are enriched in silica, alumina, sulfides, oxides, and free metals. The characterization of these slags and their con? stituent phases is an essential step in considering the ultimate use or disposal of such slags and in understanding how to alter the properties of the slags to optimize the efficiency of gasifiers. Depending upon temperatures and bulk compositions, quenched slags typically consist of silicate glasses, calcium silicates, iron-nickel oxide-sulfide masses, aluminate spinels and free metals. Whereas the glasses contain relatively uniformly dispersed metals and sulfur, the iron-nickel oxide-sulfide masses highly concentrate nickel and sulfur. The aluminate spinels very effectively concentrate vanadium and chromium, thus depleting glasses or other adjacent phases. The abundance as well as the make up of the slags strongly affects the physical behavior of the slags within the gasifiers

Jan 1, 1989

By Colin Dessemond

Since 1950, the traditional process has been dominating the production of lithium compounds from spodumene ores to sustain the lithium market because of its economic viability and the markets need for technical grade (99.5% purity) product. This traditional process includes thermal conversion, acid roasting and lithium leaching. However, this process has not been challenged and very few studies have tried to explain its limitation (95% lithium yield) or optimize the thermal treatment. Here, α to β spodumene conversion and lithium extraction were performed in a rotary kiln on a 2 mm to 2 cm spodumene concentrate instead of a micrometric one using a 1050 °C, 30 min conversion treatment and 250 °C, 30 min, 30% H2SO4 excess leaching treatment. X-Ray Diffraction analyses were performed on the converted material to determine the conversion rate by Rietveld analysis. It was observed after thermal treatment that the α-spodumene particles fractured and divided while the impurities remained compact. A sifting was performed after thermal treatment and it was determined that 65% of the initial mass became finer than 180 μm. X-Ray diffraction analyses and lithium content measurement were performed on both fractions and it was determined that the finer fraction had a very high lithium content of 3.24 wt%. Lithium extractions were performed on both fractions separately. While the coarser fraction’s lithium yield was only 61% the finer fraction’s lithium yield went up to 99% without any additional treatment. These observations may open more economical ways for the traditional process by potentially bypassing two third of costly steps such as grinding.

By John Hanna

The University of Alabama Mineral Resources Institute (MRI) has developed a unique process for selective fatty acid flotation of carbonate gangue from sedimentary apatites (francolite) in the pH range of 4-6, without collector conditioning of the pulp. The process, which does not require an apatite depressant, was modified to beneficiate a high MgO siliceous phosphate matrix from South Florida. The modified process includes two flotation stages, one for carbonate removal, as mentioned above, and the other for phosphate recovery from the siliceous gangue. The selective flotation separation of the carbonate and phosphate from siliceous constituents of the matrix at various pH levels and collector dosages are discussed. In the carbonate flotation stage, about 70% of the MgO was rejected in the froth, and the phosphate flotation stage produced concentrates analyzing about 31% P20S' 0.7% MgO and 4% acid insolubles. The overall P20S recovery in the two stages is about 85%.

Jan 1, 1989