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By M. M. Sadawy

"The increased rate of exploitation of iron ores has resulted in a rapid depletion of high-grade iron ore deposits in Egypt. New iron reserves have to be discovered to secure the iron ore for steel production. This paper aims to study the characterization and magnetic separation of low grade Aswan iron ore. The results showed that Aswan iron ore is composed of oolitic hematite, goethite, quartz and kaolinite. The screen analysis indicated that Aswan iron ore had a uniform distribution of iron and silica in the different particle size fractions and there is no any particle size has high amount of iron or low content of silica. On the other hand the results of dry high intensity magnetic separation illustrated that this technique is not suitable for upgrading this ore.IntroductionIron is one of the common metals used in industry, as well as being the fundamental raw material used in iron-steel industry; products are wide spread even in daily uses. The total iron ore reserves of the world have been estimated as 3 70 billion tones; 160 billion tones is classified as economical, while 210 billion tones as potentially economical [1]. An estimated 98% of the iron ore exploited in the world is used in the manufacture of pig iron and steel, which are non-substitutable backbones of modem society. The rapid increase of world steel production over the last few years have required an equal increase in iron ore production, from 876.8 Mt in 2006 to 948.1 Mt in 2007 [2]. The increased rate of exploitation of iron ores has resulted in a rapid depletion of known high-grade iron ore deposits. This, in turn, has led to a dramatic increase of prices. In the absence of any major new discoveries of high-grade iron ore deposits, mining companies have turned to lower-grade materials to assess their beneficiation potential to expand their production base and beneficiation capacity, in order to satisfy future demand. Egypt is going to face shortage in iron production, consequently new iron reserves have to be discovered to secure the iron needed for the country [3]. Exploitation of low grade ores requires special equipments and techniques for recovery of minerals values. High gradient magnetic separators offer promise and great potential of application both technologically and economically in the processing of fine particles containing weakly or feebly paramagnetic components [4-6]. Within this existing framework, this research was initiated to assess the beneficiation potential of low-grade Aswan iron ore by high intensity magnetic separation."

Jan 1, 2013

By Carl W. Dalrymple

A wide variety of contaminants (heavy metals, suspended solids, colloids, oils, organics) have been successfully removed from wastewater using an electrocoagulation process. An innovative electrocoagulation system is described. This process involves a procedure which subjects dissolved and suspended wastewater contaminants to the simultaneous addition of metal ions in the presence of direct current. During the treatment process Ionic and other charged particles in the wastewater are neutralized with oppositely charged ions generating the coagulation of contaminants: The process Is called CURE, and' presented here with application to wastewaters containing mainly heavy metals.

Jan 1, 1995

By M. Tokumasu, T. Mutoh, Y. Sugawara

"In October 1986, a process computer was introduced in order to achieve an optimum combustion of pulverized coal at the reverberatory furnaces. The secondary combustion air volume is controlled based on the nitrogen oxide concentration of the off-gas from the reverberatory furnaces. The carbon monoxide concentration has strong relation with the concentration of nitrogen oxide under the situation of using alternative fuels, such as chipped tires and p,ulverized coal. Using this computer aided combustion control system, both nitrogen oxide and carbon monoxide concentrations were stabilized and conventional monitoring and controlling apparatuses were absorbed into this computer system. Due to this easily operated system, labor cost was reduced and the operation of the reverberatory furnaces and the off-gas treatment plant became stable.IntroductionOnahama Smelter and Refinery started its operation in April 1965 as a large scale copper smelter and refinery in Japan. The green charged reverberatory furnaces were introduced and bunker C oil was chosen as the fuel for the reverberatory furnaces. After the oil crises, Onahama was forced to use cheaper fuels such as coal and waste tires, i.e., alternative fuels instead of the expensive oil. As the amount of the alternative fuels fed to the reverberatory furnaces increased, the concentrations of nitrogen oxide and carbon monoxide in the off-gas became unstable. Consequently, the fluctuation of the combustion condition became not to be negligible in view point of a combustion efficiency and pollution regulations. A process computer has been introduced to overcome these off-gas troubles and to reduce the operating cost of the smelter.Outline of Operation HistoryInitially, the operation started by one reverberatory furnace and then the capacity was expanded almost twice by additional furnace in December 1972. As shown in Figure I, the smelting throughput was depressed after oil crises in 1973 and 1978. From 1983 to 1985, some copper mines stopped their operations because of low price of copper metal. During this period, Onahama suffered from the shortage of concentrate production levels were depressed."

Jan 1, 1989

By Susumu Okabe

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

Jan 1, 1998

By M Phil Schwarz

"A CFD model for the gas-side of an impinging jet iron bath reactor has been developed to assist in the interpretation and design of oxidizing gas-melt reaction rate experiments. Heat transfer and reaction at the surface have been included. A free surface model, which solves for the liquid motion within the bath as well as the gas motion above the bath, has also been developed. This model also predicts extent and shape of the dimple formed on the liquid surface by the impinging jet. Both models have been run for conditions typical of jet impingement experiments using CO2 , H2O and O2• The main conclusions are• Results from the model for gas-side mass transport are in good agreement with the empirical correlation of Belton and Belton (1980)• Experimentally determined rates of decarburization by CO2 should be corrected for mass transfer because the experiments are often carried out under mixed rate control, eg for gas flow rate 10 L/min when the sulphur concentration is lower than 0.045• If the rate constant for oxygen reaction is greater than about 5 mol/m2.s.atm, it cannot be determined using a gas flow rate of 10 L/min or lower because of mass transfer control.• A cavity of depth 4.5 mm is predicted for a gas flow rate of 10 L/min and this substantially changes the flow field (and hence reaction rate) compared with a simulation in which the surface is assumed to be flat."

Jan 1, 1999

By Kang Wan, Lei Tang, Jianchao Li, Jieyu Zhang, Minqi Sheng, Jifang Xu

"The viscous flow phenomenon in slag close to the liquidus temperature was considered. A simple approach that liquidus temperatures of melt could be derived from viscosity data was employed. The potential of this method for estimating the liquidus temperatures of pure water and binary alloy was demonstrated. The liquidus temperatures of the CaO-Alz03 based slags obtained from the second derivative method depends upon the number of viscosity values available at different temperature intervals. The results indicated that plots start deviating from the straight-line behavior at temperature as expect, and the second derivatives show the break points at a certain temperature, which is the liquidus temperature. Comparisons among the present observations as well as the characteristic temperature of the selected slags, which measured by the hemisphere method and DSC, indicated that it is possible to get a reasonable idea of estimate the liquidus temperatures from activation energies for viscous flow.IntroductionThe liquidus temperature of slag, which has a significant effect on the kinetics of chemical reactions and the slag-metal separation, is extremely important for metallurgical operations. Experimental measurements of the liquidus temperatures of slags are difficult, since slags invariable supercool. In addition, behavior of a single constituent in a multi-component slag is different in different circumstances due to its interaction with other constituents. Hence, it is essential to study the liquidus temperature of each particular slag resulting from a special process. Usually, the compositions of the slags aimed to the single liquid region of the phase diagram. However, the phase diagram of many slag systems, which back often to the 1950's, involves considerable uncertainties. Many liquidus temperatures are given as dotted lines in Slag Atlas [1]. Disagreements between the phase diagram and the reality have been found [2]."

Jan 1, 2013

By Sridhar Komarneni

"Microwave-hydrothermal processing is a novel technique which combines the conventional hydrothermal processing with microwave field and we previously showed for the first time, that ceramic powders can be rapidly produced by this technique. This review paper deals with the synthesis of unary oxides such as Fe203, Ti02, Zr02, etc., binary oxides such as BaTiO3, SrTiO 3, PbTiO 3, SrZrO 3, KNbO3, etc., and ternary oxides such as NaTi2 (PO4)3 and pyrochlore phases of Pb(Mg1/3Nb2/3)O3, Pb(Zn1/3Nb2/3)O3 etc. and metal powders such as Cu, Ni, etc. below 195°C. This method can be adopted to the synthesis of a large variety of powders by the appropriate control of pH, Eh, temperature/pressure and concentration of chemical species. The main advantages of this method compared to conventional hydrothermal processing are (a) it increases the kinetics of reaction by one to two orders of magnitude, and (b) it can lead to novel phases especially those with layered structures.IntroductionConventional hydrothermal processing is a well-established synthesis technique which has been extensively used in the preparation of fine ceramic powders [1-5], large single crystals [6-8] and massive cement blocks [9]. Technologically important ceramic powders such as BaTiO 3, Al203 etc. made by the hydrothermal process are now commercially available. Although there are numerous methods for materials synthesis, hydrothermal method is truly a low temperature and environmentally benign process. For example, ZrSi04 (Zircon) which is extensively used in ceramic industry can be prepared hydrothermally at 150·C [10] compared to sol-gel or solid-state method [11,12] which require a temperature of about 1000·C. The hydrothermal method is environmentally benign because hydrothermal reactions are carried out in closed systems at low temperatures and the contents can be recovered and recycled after cooling to the ambient conditions. One of the disadvantages with any low temperature processing method is slow kinetics. For this reason we have combined the hydrothermal method with microwaves to enhance kinetics and we named this method as ""Microwave-hydrothermal"" processing [13- 16]. Although the combination of microwave and hydrothermal techniques has been used in the past few years to dissolve all kinds of inorganic (e.g. alumino silicate rocks) and organic materials rapidly for chemical analysis, we were the first to show its potential value for the synthesis of various ceramic powders [13-16]. In this paper, I show that this novel method is applicable to the synthesis of all unary, binary and multinary oxides by the appropriate control of pH, Eh, temperature, pressure and concentration of chemical species. In addition, this method is also found to be useful for the preparation of metal powders."

Jan 1, 1994

By A. D. Besser

The world production of lead has been growing continuously and reached over 7 million tonnes in 2005. At the same time, the structure of lead consumption has changed: the use of lead compounds to liquid fuel has been virtually terminated; the proportion of lead for manufacture of lead-acid batteries has been growing and reached 76.7% of the overall world production of this metal. This has taken place against the background of increasingly stringent environmental norms and environmental legislation. This is due to the lack of an alternative for lead in manufacture of local power sources. A solution to the problem of meeting the industrial demand for lead with simultaneous reduction in the primary lead production is in recycling. A large amount of batteries manufactured worldwide and their short life cycle, as well as the positive economics and a possibility to comply with the environmental requirements encourage the development of secondary lead production. Currently, over 60% of the world demand for lead is met due to recycling. The current situation with collection, transportation, storage and processing of spent lead-acid batteries has been analyzed in this paper. Examples are given to illustrate technological and equipment solutions and trends for improvement of secondary lead production discussed.

Jan 1, 2006

By M. A. Vera

This paper proposes a simple two-parameter model for the typical inverse relationship between recovery and flotation concentrate grade. The model is based on the mineralogical limitations imposed by the material properties. One parameter (R*) describes the proportion of metal content which is floatable, and the other (b) is the rate at which the fastest floating particles are being contaminated by the other less valuable particles present in the mineral system. One significant feature of the recovery-grade curve is that initial recovery (i. e. R ? 0) is at the purest attainable mineral grade, (but as recovery rises the cumulative grade of the concentrate tends to the feed grade. The ideal recovery-grade curve for a particular mineralogical system can be obtained by release analysis: the release analysis curve determines the maximum or limiting separation efficiency. The model proposed in this work is similar to the linear recovery - cut-off grade model of Dell (1), but has the advantage of describing the whole curve.

Jan 1, 1999

By G. A. Irons, G. S. Hanumanth

A three-dimensional mathematical model for the electric furnace of Cominco's Kivcet process was developed to compute the electric field intensity, power dissipation, temperature and velocity distributions in the furnace. A number of simulations of the electric furnace operation were carried out for various electrode immersion depths and electrode currents. The results showed that the current penetrated the bullion layer, generating high current densities in a layer approximately 0.3 m thick located in the slag/bullion interface region. An increase in the electrode immersion depth increased the furnace power as well as slag temperatures, and generated more vigorous bubble stirring and thermal homogeneity in the slag. For a given applied current, the computed power was in reasonable accord with the measured power input. The calculated temperatures were in rough agreement with the tapping temperatures of slag and bullion.

Jan 1, 2000

By B. I. Hop

The f10wfield set up by the standard Hydro gas purging unit has been predicted by a numerical model. In addition turbulent trajectories of gas bubbles released from the rotor are predicted. Here the deposition rate of inclusions on the bubble surface is allowed to depend on local conditions. Bubbles passing regions with strong pressure gradients, such as close to the rotor, will experience large slip velocities and large deposition rates. This model can deal with any distribution of bubble sizes and inclusions. The results found from the multidimensional flow predictions are discussed in relation to what can be obtained from a much simpler metallurgical engineering approach. The differences between these two approaches to predict the same process will be discussed. The model predictions are compared to experimental results for removal of SiC-particles from aluminium.

Jan 1, 1996

By Fernando Castro

Electric furnace steelmaking dust is a polluting residue that needs to be treated in order to recover metals contained and to produce an environmentally acceptable residue. Some hydrometallurgical approaches for its treatment have been evaluated, namely: caustic soda leaching followed by electrolytic recovery of zinc, ammonia leaching followed by zinc compounds precipitation and acetic acid leaching followed by lead, zinc hydroxide and gypsum precipitation.

Jan 1, 1992

By Sergei A. Degterov

A thermodynamic database for the slag, matte and liquid copper phases in the Cu-Ca-Fe-Pb-Zn-Si-O-S system has been developed for the ranges of compositions of importance to the production of copper. When used with the Gibbs energy minimization software and other databases of the F*A*C*T thermodynamic computing system, this database will permit the calculation of matte-slag-copper-gas phase equilibria that take place during copper smelting and converting. The calculations reproduce within experimental error limits all available experimental data on phase diagrams, activities of components, enthalpies of mixing, matte - alloy miscibility gap and tie-lines. The calculated solubilities of Cu in both S-free slag and slag equilibrated with matte are also in good agreement with experiment under all studied conditions, such as at SiO2 saturation, in equilibrium with Fe, Cu or Cu-Au alloys, at fixed oxygen or SO2 partial pressures and at different contents of Pb, Zn and CaO in the slag. Sulfide contents (sulfide capacities) of the slags are predicted within experimental error limits. The distribution of Pb and Zn among matte, slag, copper and gas has been calculated. The calculations are in good agreement with experimental data and predict the distributions under conditions which are difficult to study experimentally, such as at magnetite saturation or under various oxygen partial pressures and iron to silica ratios in the slag.

Jan 1, 1999

By Richard B. Stein

Bechtel's BEMSIM computer program is a useful tool for solvent extraction-electrowinning plant design optimization. Its power (up to 90 stream components, 240 process streams, 180 process steps) has been applied to investigate floweheet configurations in order to perform basic engineering, sizing of plant equipment and to optimize performance of commercial-size copper plants. Flowsheet variations presented include series, parallel and series-parallel extraction stages, while heat balances simulate operations in summer and extreme winter conditions. The BEMSIM program has also been applied to nickel-cobalt, gold and manganese extraction.

Jan 1, 1993

By M. A. S. Siraa

A program of work was undertaken at the Kennecott Smelter and Refinery to model the complex. This effort contributed a total of eight models of the plant: flash smelting furnace, flash converting furnace, slag concentrator, anode furnace, offgas scrubbing system, acid plant, hydrometallurgical dust treatment plant, and the precious metals plant. Some of these models have been used in a variety of investigations ranging from offgas capacities for a steam generation analysis to an examination of impurities. The culmination of this enterprise has resulted in an on-line control scheme for the flash smelting and flash converting furnaces. These two process control schemes incorporate their respective steady-state heat and mass balances that are executed in response to feed changes while a feedback loop calculates when product grade and temperatures deviate from setpoints. This system has been put into place to improve furnace control and on- line time.

Jan 1, 1999

By Marko Suput

Titanium is a high-strength, low-density metal nearly immune to corrosion, but limited in use by its high price. The high price is due to the cost of smelting and processing the ore. The research on titanium production using the Solid Oxide Membrane (SOM) process aims to consolidate most of the processing steps required for conventional titanium production into a single step making it an energy-efficient and cost-effective method for producing CP billet and ingot and possibly also powders used to make titanium alloys. In the SOM process experiment, a steel crucible contains MgF2-CaF2-TiO2 flux; an inert metal/carbon rod serves as the cathode; an oxygen-ion-conducting yttrium-stabilized-zirconia (YSZ) membrane in the form of a one-end-closed tube contains either a liquid metal that acts as the anode or liquid MgF2-CaF2 ionic flux that connects the YSZ membrane to an anode. During electrolysis, when the voltage between anode and cathode is higher than the reduction potential of titanium oxide, titanium ions are reduced at the cathode and the oxygen ions pass through the YSZ membrane and are oxidized at the anode. The oxygen ions are oxidized at the anode by a reducing agent, hydrogen gas or carbon, forming steam or CO(g), respectively. To date, a suitable MgF2-CaF2-TiO2 flux has been selected and the operating temperature for the SOM process has been determined. Several electrolysis experiments have been performed. As expected, lower valence deposits of titanium oxides have been witnessed at the cathode prior to depositing pure titanium. Continuing work will aim to extend the electrolysis time in order to pass enough charge to produce a significant amount (100 g) of titanium at the cathode.

Jan 1, 2006

By Jing Zhong, Yugang Li, Chen Yan, Shaoda Zhang, Qian Wang

Online surface quenching technology has been developed for the hot charging process to prevent the surface cracks in high strength low-alloy steel slabs. In this paper, a two-dimensional heat transfer model of surface quenching process was presented. This finite element model includes nonlinear thermodynamic properties, by which the slab temperature distributions were computed. The model predicted temperatures show reasonable agreement with the measurements. The effects of the water flow rate and slab movement velocity on temperature variation during the quenching and subsequent tempering process were investigated. The result shows that the temperature drop increases but the tempering temperature changes slightly with increasing water flow rate and decreasing slab velocity. Keeping the slab movement velocity at 1.2-2.1m/min and the water flow rate at 55-70m3/h, the slab surface experiences a temperature drop of 400-600 firstly, then recovers above 650, the quenching and energy-saving effect are remarkable.

Jan 1, 2015

By A. V. Tarasov

In order to improve the efficiency of hydrometallurgical processing of pyrrhotite concentrates, an integrated set of research has been carried out to investigate the use of sulfur dioxide in individual unit operations and as a leaching agent in the autoclave process as a substitute for oxygen. Treating iron-containing raw materials for production of nonferrous metals are based on the selective reaction of SO2 with iron sulfides and oxides. Iron is dissolved as sulfate, which can be treated in a separate circuit to produce iron-containing pigments or it can be disposed of after neutralization. Nonferrous and precious metals contained in pyrrhotite concentrate do not react with sulfur dioxide and remain virtually completely in the solid phase, i.e. high-grade sulfide concentrate to be treated by hydro- or pyrometallurgical methods. Elemental sulfur formed in the process of leaching is separated from the pulp in granulated form as a result of the use of special surfactants. The process of sulfide concentrate leaching with the use of sulfur dioxide is conducted at temperatures above the sulfur melting point (119°C) with distributed feeding of surfactant and under a partial pressure of sulfur dioxide of up to 0.3 to 0.5 MPa.

Jan 1, 2006

By Tatsuo Inoue, Marnoru Mizuno, Toru Matsuoka, Kenichiro Abe

"The distribution of particle reinforcements and the residual stresses in metal matrix composite are simulated by considering the motion of particles and the solidification of matrix associated with temperature variation in the course of centrifugal casting process. In the analysis, a heat conduction equation including heat generation due to latent heat and also mechanical work as well as heat input from successively accumulated element on the air/metal boundary is solved by the finite element technique. After the movement of particles subjected to the centrifugal force and drag are analyzed, the residual stresses are elucidated by using a unified constitutive equation which can describe the behavior both in liquid and solid states. Results of the simulation are compared with the experimental data, and the validity and utility of the procedure is confirmed.IntroductionProcess simulation of metal matrix composite (MMC) is required to determine the mechanical properties of the materials and the efficient process and conditions of the fabrication. Properties of bonding matrix with reinforcements in the course of the processing, for example, affects the strength of the composite, while the final costs of the productions depends on the efficiency of fabrication. Therefore, the simulation of processing of MMC is prerequisite in order to clarify the mechanism to fabricate the material which has been expected to maintain high mechanical properties and the cost performance.Some techniques of processing MMC[l] have been developed so far. Among them, the centrifugal casting technique [2-5] has many attractive characteristics as processing of the MMC: The centrifugal casting technique makes the reinforcements such as particles or short fibers to be distributed in the radial direction by the centrifugal force acting on reinforcements due to the difference in density between reinforcements and matrix. Since the distribution of reinforcements affect the mechanical properties of MMC, the composite with functionally gradient mechanical properties can be provided by the centrifugal casting technique."

Jan 1, 1994

By Katragadda Sarveswara Rao

"In view of the increasing importance of processing lean ores as potential future resources, efforts are being made worldwide to develop suitable technologies for the recovery of both nonferrous, base and precious metals. There are various types of low grade ores present in many countries. Gradually, the mineral reserves for production of metals have undergone complex changes with regards to their grades and particularly the physical and chemical properties of the minerals to be separated from each other. So, there is a need for new processing routes or the upgrading of existing technologies to recover metal values that are otherwise unutilized. Accordingly, an overview of the different types of mineral resources and economical processes, based on ore horizons, consumption of energy and reagents and environmental concerns, is made in this paper. In addition, the paper provides a summary of metallurgical and engineering challenges to be overcome when implementing new technologies and concepts with regard to base metal extraction and sulphur removal efficiency.IntroductionLow grade multimetal complex sulfide ores are likely to become an importance source for nonferrous as well as precious metals in the near future. The principle metallic minerals are chalcopyrite, sphalerite, galena, pyrite, pyrrhotite, arsenopyrite, tetrahedrite, boulangerite and cassiterite. Such ores are located throughout the world as multi-pocketed reserves which have present complex challenges with regard to their grades and particularly the physical and chemical properties of the minerals to be separated from each other. Their compositions can vary widely from one deposit to another and even from one location to another in the same deposit, and this poses a problem for the recovering metals present therein. Successful aqueous processing of complex sulphide ores depends on the composition and mineralogy of the raw materials and on their leaching behaviour."

Jan 1, 2012