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By E. J. Peuraniemi

Primary copper production using suspension smelting techniques like Outokumpu Flash Smelting always causes some dust formation. Flue dust particles are formed when sulphide feed material reacts violently with oxygen inducing particle disintegration and total desulphurisation of fragments. In the process, flue dust follows the off-gases to the heat recovery boiler (HRB) where its sulphation takes place because of prevailing conditions. Sulphation releases heat and causes also a drop in particle melting temperature and, further, particle sticking to the walls and heat exchange tube banks. Sulphation of synthetic CU20 particles were examined using a laboratory scale fluid-bed reactor. This study aims to a better understanding of flue dust behaviour in a HRB and, thus, to a better operational practise and design of a HRB. The effect of PSO/PO2 -ratio and temperature on the sulphation kinetics were tested. Standard chemical analysis, light optical and scanning electron microscopy with energy dispersive spectroscopy were used to examine the samples.

Jan 1, 2001

By Dao Su, Ganghua Fu, Xuling Chen, Yufeng Guo, Min Gan, Tao Jiang, Xiaohui Fan

"The sinter quantity and quality of limonite in the magnetite and hematite sintering models were studied and compared. For the sintering of magnetite, the results showed that the increase of limonite improved the permeability of sinter mixture, increased the sinter quantity and quality. The sinter strength and productivity were decreased when the proportion of limonite exceeded 50%. The appropriate proportion of limonite was 40%-50%. For the sintering of hematite, the sinter quantity and quality were first maintained at the same level thereafter declined, more obviously when the proportion of limonite exceeded 40%. The amount of calcium ferrite increased whose shape changed from acicular to leaflike and block gradually with the proportion of limonite increased from 0% to 80%.IntroductionWith the fierce competition of domestic and overseas iron markets in the twenty-first century, cheap ores such as limonite are used to be sintering raw materials to cut the costs of sinter and pig iron for steel making, and boosts the competitiveness of steel companies [1, 2]. In addition, as the reserve volume of hematite of high grade is reducing year by year, the usage amount of limonite in sintering are expanding in major domestic and international sintering plant [3, 4]. Sintering can be divided into two types, majoring in concentrates and fine ores, according to the different types of raw materials. The sintering characteristics of limonite in the two types above have been studied and compared in this paper, which makes a significant sense for the research of limonite sintering properties and guidance of ore proportioning in sintering plants."

Jan 1, 2012

By Xinhua Wang, Xuefeng Liu, Die Yang, Lifeng Zhang, Wen Yang

"CSP thin slab continuous casters are well used in recent years. The control of heat transfer in the mold is very important because it is correlated with several slab defects. The mean heat flux of CSP mold was studied based on the plant production data of LCAK steel and weathering steel. The effect of various operation conditions on the heat flux was analyzed and discussed. The results showed that the heat flux was 2.1-2.6 MW/m2 on the wide face and 1.2-2.2 MW/m2 on the narrow face for the casting of LCAK steels. During the casting of weathering steel, the heat flus was mostly 2.05-2.5 MW/m2 on the wide face and was 1.1-1.8 MW/m2 on the narrow face. The heat flux depended largely on the casting speed. The heat flux on the wide face increased obviously with increasing casting speed when the casting speed was relatively low; however, at high speed, the heat flux increased slowly or kept constant. At low casting speed, the heat flux depended little on the superheat of the molten steel. The mean heat flux depended little on the level fluctuation at continuous casting mold.IntroductionCSP thin slab continuous casters are used more frequently in recent years for its low cost of construction and manufacturing. The structure of CSP mold is very different from that of conventional thick slab casting mold, inducing the difference of heat flux between them. There have been some studies about the heat flux of thick and medium slab casters [l, 2]. Heat transfer in the mold is very important for the solidification of molten steel because it is correlated with several slab defects such as slab break-out, longitudinal crack, and surface depression. Moreover, higher casting speed is desired to improve the productivity. The control of solidified shell is extremely important. The heat flux is largely influenced by several casting parameters such as the cooling intensity of the mold, the casting speed[3], the mold flux powder [3, 4] and the carbon content of steel as well [5]. The investigation on the heat flux and affecting parameters can help to understand the solidification of molten steel in the mold."

Jan 1, 2013

By P. N. Anyalebechi

"The as-cast microstructure of two commercial-size ingots of aluminum alloy 3004 produced by the electromagnetic casting process was quantitatively characterized. This involved the quantitative determination of through-thickness and across-width variations in dendrite cell size, grain size, macrosegregation of alloying elements, interparticle spacing, and the types, volume fractions, and sizes of the constituent or second phase particles. More than ninety-five percent of the constituent phases in the ingots consisted of the A16(Mn,Fe) phase; the desirable a-Al 12(Fe,Mn)3Si phase was not detected in any of the ingots by Guinier X-ray diffraction analyses or electron probe X-ray microanalyses. A significant microstructural heterogeneity through the thickness and across the width of both ingots was observed. For example, macrosegregation, and the sizes of the constituent phase particles, dendrite cells, and grains increased concomitantly from edge to mid-width and from surface to center of the ingots. There was a -20% depletion (negative macrosegregation) of Mg and a +54-87% enrichment (positive macrosegregation) of Ti in the center of the ingots. With the exception of grain size, there was no significant microstructural difference between the two ingots examined. The causes and practical implications of the observed microstructural heterogeneity in the ingots are discussed.IntroductionThe first step in the fabrication of majority of wrought products of aluminum and its alloys is the casting of large ingots or billets of simple shapes (round or rectangular). The sizes of the ingots vary from 10 mm to 450 mm diameter or 25 mm to 780 mm thick. The quality of the finished products is established at the ingot casting stage. This is because the microstructural characteristics, such as secondary dendrite cell size or arm spacing, amount of alloying elements retained in solid solution, macrosegregation, and the characteristics of second phases, produced during casting cannot be reversed by subsequent processing. Up until twenty-five years ago, the effect of as-cast microstructure of large ingots on the structure and behavior of thin sheets (0.34 mm thick) during drawing and ironing processes was incorrectly assumed to be minimal or nonexistent. This was based on the erroneous notion that the thermal treatments and large reduction (>99.94%) and strain that the ingot undergoes during production of the sheets completely destroys the original ingot structure and its inherent heterogeneity. However, the effects of ingot structure can, a priori, be deduced from the observed effects of constituent phase particle size, type and volume fraction on recrystallization, development of texture during annealing and deformation, and earing. In fact, careful examination of the behavior of products produced from different size ingots or castings have shown that the original microstructure of the ingot has a direct impact on the properties and performance of the end products."

Jan 1, 2011

By Lucas Nana Wiredu Damoah, Lifeng Zhang

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

Jan 1, 2012

By I. Gaballah

The kinetics of oxychlorination of pure CI-2O3 with C12+02 gas mixtures is studied by ThermoGravimetric Analysis (TGA) in non and isothermal conditions up to 1000 °C. The reaction of Cr2O3 with C12+O2 chlorination gas mixtures starts at about 550 °C and the reaction product is CrO2Cl2. The oxychlorination rate of Cr2O3 is almost proportional to the chlorine partial pressure and to the fourth root of the oxygen partial pressure in the chlorinating gas mixtures. At 800 °C, the maximum chlorination rate is obtained using a gas mixture having a C12/O2 ratio equal to 4. The apparent activation energy of the oxychlorination reaction of Cr2O3 is 87 and 46 kJ/mol at temperatures lower and higher than 650 °C, respectively. By varying the chlorine and the oxygen partial pressures of the oxychlorinating gas mixtures at temperatures higher than 550 °C, it is possible to extract selectively the chromium chlorinated compounds from the chromium bearing materials. a. Laboratoire Environnemem et Minéralurgie, BP 40, 54501 Vandceuvre, France, b. École Nationale Supérieure de Géologie, Rue du Doyen Marcel Rouhault, 54501 Vandoeuvre Cedex, France, c. Centre National de la Recherche Scientifique, 3 rue Michel - Ange, 75794 Paris Cedex, France, d. Insritut National Polytechnigne do Lorraine, Rue de la Font de Haye. 54501 Vandceuvre Cedex, France.

Jan 1, 1997

By Qian Li, Haiyan Leng, Kuo-Chih Chou, Haoyuan Xiao, Zhigang Yu

Magnesium borohydride and Magnesium alanate were synthesized by mechanochemical metathesis reaction. The thermal decomposition behaviors of Mg(BH4)2-nMg(AlH4)2(n=0.5,1) systems were investigated as potential hydrogen storage materials. The results showed that the systems started to desorb H2 at 120 ℃ and desorbed 3.9 wt. and 4.9 wt.% H2 below 300 ℃ when n equals 0.5 and 1, respectively, while individual Mg(BH4)2 started to desorb H2 at 250 ℃ and desorbed only 0.82 wt.% H2. Because of the exist of the Mg(AlH4)2, the isothermal desorption kinetics of Mg(BH4)2 in the Mg(BH4)2-0.5Mg(AlH4)2 systems was 50% faster than that of pristine Mg(BH4)2. In addition, the re-hydrogenation rates also increased 49.4% and 37.9%.

Jan 1, 2015

By S. W. Marcuson

Smelting of nickel-copper sulfide ores at Vale Inco’s Sudbury operations commenced in 1888 and the first converting plant went into operation in 1892. As the demand for nickel grew, the smelting operations expanded and by the 1960’s the Copper Cliff Smelter featured the longest converter aisle in the world with space for nineteen Peirce-Smith converters. During this long period, different converting techniques and vessels were employed. The evolution of converting is reviewed with special emphasis on the modifications made to the Peirce-Smith vessel to accommodate the metallurgical and process needs of the changing times.

Jan 1, 2009

By Zhao Guangwen, Wu Tan, Qiuzhan Tian, Duan Shuzhen

"A thorough study of lost currents in bipolar cells has been made for the development of the great potential of bipolar cells in energy saving. A proper equivalent circuit for bipolar cells has been found, and mathematic methods for computing lost currents at all kinds of polarization have been developed.At linear polarization, the lost currents can be computed by solving either a tridiagonal matrix or an ordinary differential equation of second order. This kind of values can be used to evaluate the minimal lost currents at given conditions. At other kinds of polarization, the lost currents can be computed by the same methods as above if the necessary experiments of measuring the cell voltages of every electrolytic compartment have been made. This kind of values can be used to design bipolar cells at practical conditions.Extensive experiments have been made to evaluate the effects of electrode polarization, emf of galvanic cell for the formation of electrolyzed substance, gaseous products, geometric dimensions of electrolytic cells, special resistance of electrolyte used, and the total and ordinal number of electrolytic compartments on lost currents. It is the first time to make such a systematic research by experiments in the world. Experiments showed that theoretic models were in good agreement with measured data. Experiments also showed that D.C. energy consumption of 0.45 kwh/kg of Pb for lead electrolysis from molten chlorides could be achieved in a cell with 7 bipolar electrodes.IntroductionIt is very promising to apply bipolar electrolytic cells to electrolysis of aluminum, magnesium, lead, zinc and perchlorinates for their great potential of energy saving for example, bipolar cells had been used in the production of magnesium and saved more than 30% of energy, being one of the three main techniques of energy saving in the production of titanium sponge (1)."

Jan 1, 1988

By Avijit Moitra

The behavior of the solidifying shell in the early stages of solidification has an important influence on the final quality of continuously-cast steel slabs. In order to understand the thermal and mechanical behavior of the shell, a two-dimensional transient piecewise-coupled finite-element model has been developed. The model simulates a transverse section of the slab as it moves down through the mold and incorporates the effects of heat conduction, solidification, shrinkage, turbulent fluid flow, thermal distortion of the mold and the visco-plastic behavior of the steel. Coupling between the thermal and the mechanical model is based on the mutual dependence of heat transfer across the interface between the shell and the mold and the size of the gap. The effects of mold distortion and taper on the gap size are also included. The effect of fluid flow has been incorporated via a heat flux imposed at the solid-liquid interface, which is obtained from a separate fluid flow model. The high temperature creep and plasticity of the steel is incorporated through a unified constitutive law defining the inelastic strain rates as a function of temperature, time and stress state. The model can be applied to various problems in continuous casting, such as the formation of surface defects and the design of mold taper.

Jan 1, 1992

By E. T. White

The population balance is one of the basic relations for a:n:aIysing particulate minera1 processing operations. It is an exact relation. The principles of the population balance are reviewed and applications in the minerals industry discussed.

Jan 1, 1996

By A. Christlo

Short circuit detection in 1984 involved nine inspectors for production rates of 43,000 tpa. Trials indicated the feasibility of applying cell voltage monitoring to short circuit detection and improving operational efficiency. A computerised cell voltage monitoring system was commissioned in February 1986, to read voltages from 648 cells. The system incorporates 16 evenly distributed work face units which communicate with a central computer system. Provision has been made in the computer program for the automatic adjustment of cell reference voltages. This allows for the effect of polarization and other process variables which might other wise interfere with short circuit detection. The work face units can continue to work independently for several days should this become necssary. Current efficiencies have been maintained and the number of inspectors reduced from nine to five.

Jan 1, 1987

By Hao Rang

The article Is specially to Introduce the recovery process of Nb, Mn, P from slags and reutilization techniques of the remaining slags. Nb-Mn-Fe alloys which contain 14-16% Nb, 40-60% Mn can be obtained after using fire refining process of " Blast Furnace-Revolving Furnace-Electric Furnace -Electric Furnace, "meanwhile, phosphorous slags which the content of phosphorus pentoxide Is 29.21%. Further going through wet metallurgical processing and electrowinning technics to recover grading 99°o metallic manganese. Finally, phosphorous slags are grinded finely to be as phosporous fertilizers to be directly used for farmlands. Small particle size (0-8mm) rich slags are mixed with slight solid additions for balling directly, and taken Into blast furnace with blocky slags all together. The remaining tall slags are fully used as constructional materials, slags cement as well as a serial of wall materials, road materials, ground ornamental materials without burning operation and steam curing. The compressive strength range of those materials is up to 15-30 MPa. There is no more solid waste slags effluent In the full technical process.

Jan 1, 1994

By Saeid Pournaderi, Ahmet Geveci, Ender Keskinkilic, Yavuz A. Topkaya

There are mainly three commercial nickel laterites in Turkey: Gordes, Caldag and Sivrihisar. The first two appear in Western Anatolia. The third one, Sivrihisar (Yunusemre) laterites have been found in the first decade of the millennium, in the Central Anatolia region of Turkey. Since then, mining facilities have been continued in Yunusemre. Calcination, prereduction and smelting of Sivrihisar laterites have been extensively studied and published. In the current work, some results of the studies related to characterization of Sivrihisar laterites will be presented.

Jan 1, 2016

By Fujio Ishii

The deoxidation of liquid nickel and nickel binary alloys with silicon has been determined at temperatures between 1500°C and 1650°C using quartz crucibles in order to investigate the deoxidation of nickel based alloys. The equilibrium constant of the deoxidation reaction in liquid nickel and the effects of the different alloying elements such as chromium, molybdenum, tungsten, iron, cobalt and coppcr on the activity coefficient of oxygen in liquid nickel have been established.

Jan 1, 1993

By T. T. Chen

Gold in the Twin Creeks ore is primarily associated with arsenian pyrite. During pressure oxidation, the sulphides are solubilized, but part of the dissolved iron reprecipitates as jarosite and as an iron sulphate-arsenate-phosphate phase. The pressure oxidation products are subjected to cyanide leaching. The cyanide leach residues consist of quartz, gypsum, bassanite, anhydrite, small amounts of jarosite, an iron-sulphate-arsenate-phosphate phase, as well as trace amounts of orthoclase, rutile, pyrite, hematite and monazite; all these particles are dispersed in a fine grained matrix of illite-muscovite. The autoclave leach residues contain a small amount of carbonaceous matter. Many gold grains are detected on the surfaces of the carbon particles, and these gold particles are not leached during cyanidation. The gold particles are typically 0.1-0.2/Lm in size and commonly are embedded in the carbon surface or are coated with a K-AI-Si-S-O phase on the surface of the carbon. The gold grains are consistently associated with elevated CI contents (50-300 ppm Cl). The poor gold cyanide leach recoveries, which initially occurred in the Twin Creek developmental circuit under certain operating conditions, are attributed to the presence of chloride in the feed. This results in the formation of soluble gold chlorocomplexes in the autolcave and the subsequent sequestering of the gold on the surfaces of the carbon particles.

Jan 1, 2000

By D. W. Collins

The uptake of gold from halide solutions by activated carbon has been investigated using various techniques. Halide systems typically exhibit combined adsorption-reduction type behavior. In an attempt to gain more information about the nature of these processes, samples of synthetic highly-oriented pyrolytic graphite (HOPG) were contacted with aqueous solutions of gold-iodide. HOPG represents a model structure for activated carbon comprising of basal- plane sites, edge sites, and various defect sites. Two basic instrumental methods were used to examine the uptake of gold by HOPG. The first was standard X-ray photoelectron spectroscopy (XPS). The other involved several scanning probe techniques. XPS clearly indicated a preferred uptake of gold at edge sites. However, iodine appeared to be distributed on both basal-plane and edge sites. At low iodine additions, tapping mode AFM showed that clusters were concentrated along steps and surface defects. At high iodine concentrations, the HOPG surface was uniformly covered by iodine.

Jan 1, 1998

By Jewel Gomes

Green rust is an important intermediate in oxidative transformation of Fe(II) phase. This unstable compound contains a mixture of ferrous and ferric hydroxides that belong to a family of minerals known as layered double hydroxides (LDH). Its general formula is [FeII(6-x) FeIIIx (OH)12]x+[Ax/n-*yH2O] x-, where A is an n-valent anion mainly Cl-, CO3-2 and SO4-2, and in which either the bivalent or the trivalent iron can be replaced for other trivalent or bivalent metal ions. It was first identified as corrosion product, later in soils as a product of interactions between microbes and metals in soils. Due to its high reactivity, it is used in the reduction of organic and inorganic compounds, As removal, and the treatment of acid mine drainage. In this paper, we described the method of electrochemical generation of green rust, its characterization by XRD, SEM and FT-IR, and its implications to electrocoagulation.

Jan 1, 2009

By H. Tan

?Preg-robbing? is the active adsorption of gold from cyanide solution by the ore components. The role of carbonaceous coatings on chalcopyrite surfaces in the preg-robbing of chalcopyrite has been investigated by using pure chalcopyrite and a copper concentrate. Activated carbon and graphite were chosen as representative carbonaceous contaminants. It was found that the carbonaceous coatings enhanced the preg-robbing of chalcopyrite. Activated carbon coating increased gold adsorption onto chalcopyrite to a lager extent, in comparison with graphite coating. In the preg-robbing of the copper concentrate, gold adsorption was increased to larger extent at finer particle sizes and at higher contents of activated carbon or graphite. The preg-robbing of chalcopyrite was reduced or eliminated, depending on the concentrations of free cyanide. However, the gold adsorption on the carbon and graphite coated chalcopyrite could not be avoided even at higher cyanide concentrations, and this adsorption was solely attributed to the carbonaceous coatings. Zeta potential studies indicated that the carbonaceous coatings reduced the negativity of the chalcopyrite surface charge. As shown by SEM analysis, gold not only accumulated at the edges and defect sites, but was also spotted on the smooth surfaces of chalcopyrite with carbon or graphite present. XPS results revealed that gold was strongly reduced on chalcopyrite surfaces, with the sulfide ions of the chalcopyrite being oxidized to elemental sulfur. Diagnostic elution indicated three mechanisms contributing to gold take-up by chalcopyrite, i.e. gold reduction, physical adsorption and chemical adsorption.

Jan 1, 2003

By Bin Du

In recent years, concurrent product design and process is gaining popularity and will become a norm of the industry of the future. Forging has been a critical manufacturing process for production of components with superior tensile strength, toughness and grain flow. This paper describes an expen system which is being developed for forging die design and forging process analysis in concurrent engineering environment. Rules and guidelines pertaining to forgeability are formulated and incorporated into the knowledge-base in building the system. The system is built using an object-oriented paradigm. The object-oriented approach and hierarchical rule structure paradigm are briefly discussed. Finite element analysis packages (ALPID-2D) were incorporated into the program to give the simulation result of the forging process. The system can automatically produce a competent design and recommend a set of processing parameters for a given product. The designer can modify the design according to the result of the simulation.

Jan 1, 1992