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Reduction of titania and ilmenite ores by Cf4-H2-Ar gas mixture was investigated in a laboratory fixed bed reactor. Titania was reduced to titanium oxycarbide in the temperature range of 12OO-1500°C. At 1400-15000C, the extent of reduction of titania to titanium oxycarbide achieved more than 85% in 90 min. Optimum conditions for titanium oxycarbide synthesis by reduction of titania include temperature in the range of 1300-1450°C, methane content 8 vol% and hydrogen content above 35 vol%. Ilmenite ore was reduced by Cf4-HrAr gas mixture to metallic iron and titanium oxycarbide. Metallic iron catalyzed methane cracking and solid carbon deposition. Titanium oxycarbide formed at temperatures as low as 950°C. The optimum temperature for reduction of ilmenite is 1200°C and the optimum methane content is 8 vol%. Increase in hydrogen content increased both rate and extent of reduction. With 5 vol% CH4-75 vol% Hr20 vol% Ar gas mixture, the reduction of ilmenite completed in 60 min. Reduction of titanium oxides to oxycarbide with following chlorination may be an efficient alternative technology for processing of titanium minerals.

Jan 1, 2001

By T. A. Chepushtanova, B. Mishra, E. O. Kilibayev, V. A. Luganov

"The paper contains the results of studying about modification of pyrite and arsenopyrite specific surface and porosity at their thermal decomposition. The studying of specific surface was carry out by B.E.T. – adsorption of nitrogen at his boiling-point. In our work were using the electron-microscopical, X-ray structure analysis and chemical analysis. There was established that the decomposition of pyrite and arsenopyrite accompany by increasing of pores volume from 0.303 · 10-3 to 1.23 · 10-3 at increasing of pyrite degree of decomposition about 41 % and then decrease about 0.131 · 10-3 m3/g at degree of decomposition near 100 %. The surface area of pores increase from 0.31 to 1.085 m2/g with following lowering due to enlargement and confluence of minor, small pores. Increasing of porosity accompany with increasing of particles windage that appear the result of heightened dust-furnace partially decomposing pyrite and arsenopyrite particles by air flow from furnace reaction zone. This explains heightened contention of sulfide sulfur in roast dust of sulfide concentrate. 1. INTRODUCTION As a result of ore base exhaustion of ferrous and nonferrous metallurgy at metallurgical treatment are involving more complicated and less qualitative ores. Magnetiting ores content considerable quantity of pyrite complicative the technology of iron extraction. At the same time the pyrite concentrates wining at dressing content different nonferrous metals in industrial quantities. Extracting ores of nonferrous metals are contenting considerable quantity of arsenic at the present time. Extraction of base metals from complicated raw materials demands new technologies. Arsenic contenting in ores is necessary to utilize (waste burial) in more ecological compatible form. Arsenic on acting metallurgical and chemical enterprises from technological cycle is withdrawing in the form of arsenate – arsenite cakes, burial of their may lead to seriously ecological problems as times goes by. In Kazakh National Technical University is carry out the cycle of researching by pyrite, arsenopyrite and arsenate – arsenite cakes treatment with the object of arsenic withdrawal in sulfide form – in more ecological and safe form and with the object of preparation of initial ore raw materials to following pyro- and hydrometallurgical treatment. As a result of sulfidizing of arsenate – arsenite cakes by pyrite are forming the volatile arsenic forms and pyrrhotite of variable structure."

Jan 1, 2008

By Fatma Arslan

Alada (Kayseri-Turkey) lead-zinc sulfide-oxide ores contain 10.17% Pb, 10.98 %Zn, 164 g/t Cd and 57 g/t Ag. During the laboratory scale flotation tests of these ores, it was found that almost all zinc was remained in the tailings that contain 12.31% Zn, 1.35%Pb, 198.3 g/t Cd, and 22.3%Fe. Three different methods were studied such as basic (NaOH) leaching, roasting+acidic (H2SO4) leaching and direct acidic (H2SO4) leaching for recovering metals that these tailings contain. In the direct acidic leaching, which gave the best results, dissolution efficiencies of 91.5% zinc, 78.2% cadmium, and 14.3% iron were reached at the optimum leaching conditions while Pb remained in the leach residues and the acid consumption was 422.3 kg/ton of tailings.

Jan 1, 2006

By Artur Camposo, Rômulo. L. Loiola, Frederico M. Margem

"The growing interest for natural materials as an environmentally friendly alternative for the substitution of energy intensive and non-sustainable synthetic materials, has motivated the use of lignocellulosic fibers as reinforcement of biocomposites. The sisal fiber, a relatively unknown lignocellulosic fiber with potential for composite reinforcement, still needs to characterize for possible engineer applications. Therefore, the present work analyzed the sisal fiber by means of Fourier Transform Infra-red (FTIR) spectroscopy. The sisal fiber FTIR spectrum revealed main absorption bands typical of any lignocellulosic fiber. However, some specific bands as well as bands broadening and intensity suggested particular activities for functional molecular groups in the sisal fiber.IntroductionIn recent decades, environmental issues related to worldwide pollution and climate changes, mainly the global warming, are motivating new paradigms for the development of our society. Among these, the use of natural materials in substitution for non-sustainable synthetic materials, obtained from non-renewable ores and petroleum, is increasingly being considered. In particular, natural fibers extracted from plants are, in this 21st century, experiencing a surge as composite reinforcement [1-11 ], following their replacement by synthetic fibers, specially the glass fiber, during the second half of the 20th century [1-2-8].In addition to environmental benefits [12-13] the lignocellulosic fibers present economical advantages, such as worldwide abundance and comparatively low costs as well as some technical properties associated with flexibility and toughness[ll], which contribute to the performance of automobile components fabricated with natural fibers composites[14-16].Among the less common lignocellulosic fibers that only recently have been investigated[l 7], the fibers extracted from the stem of the sisal plant, shows in Fig 1, reveals a potential for polymer composite reinforcement."

Jan 1, 2013

By Nagy El-Kaddah

"One of the emerging technologies for the production of ultra-clean metals is electromagnetic filtration. The theory and the mechanism of electromagnetic separation of inclusions from molten metal are briefly reviewed along with basic electromagnetic separation systems. This paper focuses on inclusion removal in the induced current separators, with specific reference to a new separator developed at the University of Alabama. A simple analytical model is presented for the analysis of particle separation in such a system. The role of the applied magnetic field on inclusion removal will be discussed. It is shown that particle velocity increases exponentially with increasing magnetic field strength. At moderate field strengths, the velocity of 50 to 100 u. inclusions· are an order of magnitude larger than those achieved by buoyancy. The separator developed at the University of Alabama is described together with experimental results of laboratory and large scale experiments on purification of molten aluminum. These results demonstrate the capability of the system for producing super-clean metals.IntroductionThe nature of extraction, refining and processing of metals is such that oxides and other non-metallic particles will always be present. This is due to the highly reactive nature of metals with oxygen and other non-metallic elements. The presence of these type inclusions in metals, even in minute amounts, can seriously flaw the reliability and performance of the final product. They not only reduce the strength and the stiffness of the metal/1/, they are the reason behind many of manufacturing defects such as porosity in castings, surface and internal cracks in continuously cast ingots and rolled products, etc., which act to cause premature failure of manufactured parts. In fact, for critical applications such as turbine blades, there is virtually no tolerance for inclusions above ten microns in size /2/. Therefore, removal of inclusions from the liquid metal is an essential processing step.The demand for cleaner metals has brought major changes in the technology and practice of metal refining and casting. Inclusion removal from the melt is currently achieved by passing the melt through a series of melt treatment systems, including induction stirring furnaces, argon-stirred ladle, and ceramic foam and deep-bed filters /3,4/. These systems are generally capable of removing all inclusion particles above 50 microns in diameter, which meets current cleanliness requirements for most applications. However, they may not be able to meet the projected cleanliness levels for critical applications due to kinetic and operational limitations of these systems in removing smaller particles /5/."

Jan 1, 1996

By Wen-Ming Chien

Low temperature X-ray diffraction and thermal property studies of the solid-solid state phase transition for the polyalcohols (pentaerythritol (PE), pentaglycerine (PG) and neopentylglycol (NPG)) thermal energy storage solid solutions have been investigated by using X-ray diffractometry and differential scanning calorimetry (DSC) methods. X-ray diffraction studies on polyalcohols solid solutions, PE-NPG and PG-NPG, are from ?10oC to 50oC. XRD results shows the + mixed phase at the related low temperature (?10oC) for both PE-NPG and PG-NPG solid solutions. At high temperature range, XRD results show phase for PG-NPG solid solution and + mixed phase for PE-NPG solid solution. There are only two Bragg peaks, (111) and (200), shown in phase XRD patterns. The polyalcohols solid solutions have been cycled 5 times between -20oC to 100oC at different DSC scan rates to study the phase transition properties. DSC results of both PE-NPG and PG-NPG solid solutions show that the solid-solid state phase transition is near room temperature. Details of low temperature phase transition XRD and DSC results of PE-NPG and PG-NPG solid solutions will be presented

Jan 1, 2006

By Animesh Jha, Catherine Davey

"Carbothermic reduction and nitridation reactions using synthetic kaolinite mineral were investigated for the formation of silicon based nitrogen ceramics. The temperature dependence of the reaction rate and its effect on phases formed are reported. The effect of the reactivity of carbon on the kinetics of formation of AIN and ShN4 is discussed. Using the standard Gibbs free energy values for the formation of nitrides and oxides of aluminium and silicon, a log po2 verses I/T diagram is constructed. The experimental data results are discussed and compared with the predicted phase equilibria. We also report the influence of sub-oxide gaseous species on the microstructure of the ceramic phases produced.IntroductionSynthetic kaolinite is a clay containing alumina, silica and water of crystallisation, and has a chemical formula 3(Al2O 3.2SiO2.2H2O). This mineral is relatively inexpensive and, is therefore an ideal candidate for use in the production of ceramic powder mixtures for example silicon nitride and aluminium nitride for composite material formation, When the mineral is heated, the water of crystallisation from the crystal lattice is lost via the 3(Al2O 3.2SiO2.2H2O) = 3(Al2O3.2SiO2) + 6H2O reaction. It has been shown [1·2j that on further heating to 1673K, the anhydrous kaolinite decomposes to a mixture of mulllte and silica, 3(Al2O3.2SiO2) = 3Al2O 3.2SiO2 + 4SiO2 which is consistent with the alumina-silica phase diagram, shown in figure 1.The binary alumina-silica phase diagram has a well-defined sub-eutectic immiscibility dome and this characteristic dernixing behaviour is reflected in the thermal decomposition of anhydrous kaolinite consequently the microstructural features resemble the spinodal decomposition process. It is well established that the spinodal decomposition process raises the nucleation frequency due to their low free energy barrier, (?G). The small magnitude of this barrier consequently promotes the evolution of a very fine microstructure. The process of spinodal decomposition is therefore expected to be influential during the reduction-nitridation of kaolinite minerals."

Jan 1, 1996

By Mark Osborne, Ray D. Peterson, C. Edward Eckert

"The theoretical melting energy requirement for a typical hypoeutectic aluminum-silicon alloy is approximately 520 BTU/lb. It has been demonstrated, however, that even a state of the art secondary processing-automated lost foam casting operation can exceed this value by at least an order of magnitude when the actual thermal energy input from melting to solidification is monitored. Metal transfer and holding operations constitutes over 65% of this expenditure. The authors present relative benchmark energy expenditure information by unit operation for an offsite melting/lost foam casting line with a daily throughput in excess of 100,000 lbs. Efficiency improvements through optimization of the current process, and anticipated energy values at the culmination of a U.S. Department of Energy sponsored project to develop, integrate and demonstrate an advanced melting, transportation, and dispensation system will be cited.IntroductionThe size of the U.S. aluminum remelt pool was approximated to be 14.21 billion kg (31.27 billion pounds) by a recent study?, with the engineered castings (foundry) sector accounting for 3.25 billion kg (7.16 billion pounds) or 23% of that total. This study considered overall process yield and all major contributors to scrap. The values cited, therefore, are more meaningful than simply tabulating annual pounds shipped by sector.The foundry sector consists of Sand Castings, PM Castings and Die Castings categories appearing in Figure 1. All other categories comprise the wrought alloy sector. Wrought alloy production enjoys an energetic benefit from both scale and a relatively continuous operation. Many foundry operations, however, operate in batch mode at less than design metal throughput with characteristically longer melt holding periods. Since any detention of molten metal beyond melting represents an overhead use of energy, melt holding (secondary) energy expenditures can appreciably inflate melting energy requirements in the foundry."

Jan 1, 2009

By Jeff M. Kuhn

A new solvent extraction process for the removal of halides from zinc sulphate solution was tested in pilot plants at both a 0.1-L/min scale and at a 3-L/min scale. Teck Cominco?s process is called the HalogonTM process, for which patents are pending. Mixer-settlers were used for the 0.1-L/min pilot scale and two BATEMAN pulsed columns for the higher rates. Pilot testing was performed with commercial zinc sulphate solutions containing variable amounts of chloride and fluoride. Sulphate extraction was also controlled and deleterious halides were loaded and stripped into a form suitable for disposal. The engineering aspects and economics of this solvent extraction process for halide removal are also reported.

Jan 1, 2003

By Elsa Agante

Recycling of solid wastes, a common practice nowadays, requires the separation of the different materials in order to increase the products added value. The separation of one plastic from mixtures of different types of plastics is not easy due to their similar physical properties, but different techniques are available, from automatic sorting systems based on optical sensors to techniques adapted from mineral processing, namely gravity, froth flotation and electrostatic processes. In the last decade, many researchers have addressed the separation?s problem of different polymers, like Polyethylene Terephthalate (PET) and Polyvinyl Chloride (PVC), two polymers commonly used in packaging which have similar density. One proposed technique is the classical froth flotation performed in agitated cells. Froth flotation is a versatile and relatively cheap process widely used in mineral separation. It is based on the different behaviour of particles in the presence of an inter-phase air-water, which depends on the materials surfaces properties. Froth flotation can be affected by some variables such as impeller speed and air flow rate. Agitated cells, when used with low density materials, like plastics, can produce overstated turbulence that prevents the adhesion and collection of particles in the froths. In this case, separation is favoured by column flotation smoother hydrodynamics. This paper proposes the separation of PET from PVC by column flotation. The experimental work was carried out in a column of 9cm diameter and 1m high. The effects of some operating conditions, such as depressor and frother concentration, air flow rate and feed grain size on products grade and recovery were evaluated and the best flotation conditions for the separation of these plastics were established.

Jan 1, 2006

By R. A. Roberti

Most copper refineries use conventional wheel systems to cast anodes. over a period of time the copper moulds that are used become warped and cracks develop. To control mould warpage, the mould's are either rejected after a certain warpage is reached, or the shape is restored by mechanical means. The cracks, unless they are very severe, are repaired by a peening process. Even with regular maintenance to control warpage and cracks, the moulds have a limited useful life. If warpage and cracks are not controlled, anode quality deteriorates and tankhouse operations are seriously affected. -An intensive study was initiated to develop means of controlling mould warpage which culminated in the d?evelopment of technology to control mould warpage to within ±1. 5 mm, and at the same time effectively contr0l: cracking and significantly increase the mould life-. The warpage control has been achieved by using a unique mould design. Mould cavities are present on both sides of the mould and periodic inverting controls the wa-rpage in the cavities. The mould casting procedure has been developed and all production wheels have been converted to the new mould design. The performance characteristics of these moulds will be detailed. 21

Jan 1, 1987

By Minjun Tang, Jianfeng Zhou, Feng Chen, Linjiang Qing, Xiaolei Song, Yufeng Guo, Tao Jiang

"Reduction swellability index (Rsn and low temperature reduction disintegration index (RDI) of vanadium-titanium magnetite oxidized pellets are harmful to the processing of ironmaking, for example, causing serious gas permeability, decreased yield, higher coke ratio and more furnace dust. Thus, the improvements of RSI and RDI of vanadium-titanium magnetite oxidized pellets were investigated in this paper, including the pretreatment of raw material, additives of dolomite or boric acid, pellets treated in chloride solution and so on. The results showed that damp milling as pretreatment and boric acid added in pelletizing were conducive to the RSI which decreased 5% and 7% respectively, while they were not efficient enough in improving RDI. Dolomite was efficient in improving RSI, but had negative effect on RDI. There was no evidence to show that RSI and RDI would be improved when pellets were treated in chloride solution. Pursuing this further, the mechanism of those improvements were investigated.IntroductionIn the world, vanadium-titanium magnetite utilization is investigated around how to recover iron, titanium, vanadium, and divided into blast-furnace method and non-blast-furnace method according to respective characteristics. Blast furnace method [1, 2] can recover iron and vanadium effectively, but Ti02 cannot be recycled. Non-blast-furnace methods include rotary kiln-electric furnace method, pre-reduction electric furnace method, reduction- grinding method and sodium vanadium-rotary kiln-electric furnace method and so on. [3-7]Comparing to the Non-blast-furnace method, the method of blast furnace smelting has been put into industrial applications. And it has the following advantages: First of all, effective recycling iron and vanadium; Second, technical problems of high titanium slag in blast furnace smelting; Third, it has mature technology in blast furnace smelting."

Jan 1, 2013

By Ana P. Paiva, Marc F. Comella, Sandra S. Reis, Joao N. Reis, M. Soledade Santos

"In this work, the influence of the malonamide structure, acidity of the aqueous phase and diluent on the equilibrium interfacial tension (IT) of N,N'-dimethyl-N,N'-diphenylmalonamide (DMDPHMA) and N,N'-dimethyl-N,N'-dicyclohexylmalonamide (DMDCHMA) in 1,2- dichloroethane (1,2-DCE), and DMDCHMA in toluene, with aqueous HCl, were investigated. IT isotherms were determined using the Du N ouy ring method. Densities of the organic phases were determined, and used to screen solute-diluent interactions. Formation of third phases was never observed; furthermore, ITs increase with the phase separation period, constant values being obtained for separation periods larger than 1000 seconds. Each malonamide interfacial efficiency at the oil/water interface is interpreted in terms of malonamide basicity, diluent polarity and malonamide - hydrochloric acid- diluent interfacial interactions.IntroductionFor several years now, N,N'-tetrasubstituted malonamide derivatives have been extensively investigated as liquid-liquid extraction agents since they were first proposed as the organic components of the DIAMEX process, with the aim of advantageously replacing tributylphosphate in PUREX [1]. Therefore, a significant part of research studies with malonamides appearing in the literature deal with the extraction of major and minor actinides in real or simulated spent nuclear fuels in nitric acid solutions [2]. Under typical experimental process conditions, the tendency shown by some N,N'-tetrasubstituted malonamide derivatives to aggregate in the organic phase, leading in a few cases to the formation of undesirable third phases, has been remarked and consequently thoroughly investigated [3, 4]. The increasing use of chloride streams as hydrometallurgical aqueous feeds is becoming a reality, and this fact is obviously deeply founded on an extensive research carried out to recover value-adding metals from these media. Following this trend, a number of N,N'-tetrasubstituted malonamides have already been screened for the recovery of iron(III) [5, 6] and platinum-group metals [7] from hydrochloric acid solutions. The results obtained are quite promising either in terms of total metal ion recoveries or selectivity patterns achieved. The formation of a third phase when iron(III) was extracted by the tested N,N'-tetrasubstituted malonamide derivatives has never been observed under the adopted experimental conditions, and the extraction data collected would need to be reinterpreted accordingly if any aggregation phenomena involving the considered extraction systems were to take place."

Jan 1, 2011

By Zhanjun Wang, Yongqi Sun, Mei Zhang, Zuotai Zhang, Min Guo

The role of fluorine on the viscous and crystallization behavior of CaO-SiO2-MgO-Al2O3-FetO-P2O5-(CaF2) slags were explored using the rotating cylinder method, non-isothermal differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. It was found that the viscosity slightly decreased with increasing CaF2 content. It was also found that CaF2 addition can promote the primary phase transformed from MgFe2O4 spinel to Ca3(PO4)F, which was beneficial to the enrichment of phosphorus. Additionally, the structure of the slags explained by X-ray photoelectron spectroscopy (XPS) and magic angular spinning nuclear magnetic resonance (MAS-NMR) were further analyzed, which was well in accordance with the above analysis.

Jan 1, 2016

By L. Katgerman, R. Van Toi, H. E. A. Van den Akker

"Mould filling simulations are powerful tools for optimizing the characteristics of castings. The robustness of calculational methods for mould filling simulations is generally tested in simple geometries. While a vertical plate has been used often for validation studies, this paper aims at mould filling simulations of a horizontal thin wall casting. Such castings exhibit a strong interaction between heat transfer (solidification), surface tension and gravitational force.The results are presented of a study to validate numerical simulations of mould filling phenomena in a thin wall horizontal casting. Solidification during mould filling is studied computationally. Velocities are measured using Particle Image Velocimetry.INTRODUCTIONIn foundry practice Computational Fluid Dynamics (CFD) is being considered a promising tool to arrive at a better understanding of casting defects introduced during the mould filling period of a casting. The use of CFD is believed to be advantageous in predicting possible defect locations, pouring times, and the lowest possible casting temperature without the risk of cold shuts. In addition, CFD may be used to optimize pouring system geometries [1,2]. As opposed to experimental studies in, e.g., cold water models, CFD allows for the flexible modification of the casting geometry and the pouring system, and for the inclusion of physical effects such as solidification and heat transfer. Thus, a proper use of CFD may lead to a reduction of the casting rejection rate without expensive trial-and-error procedures, and to a decrease of production costs in foundries. Mould filling simulations take a special place in CFD, because a free surface tracking algorithm is required. Over the past decade methods, MAC [3] and SOLAVOF [4], have been extended to 3-D. The robustness of computational methods for mould filling simulations is generally tested in simple geometries [5,6]. While a vertical plate has been used often for validation studies, this paper concentrates at mould filling simulations of a horizontal thin wall casting. Thin wall horizontal castings exhibit a strong interaction between heat transfer (solidification), surfaces tension and gravitational force. The gravitational force in this setting is orthogonal to the plane of flow and has therefore no influence on the shape of the free surface in the plane of flow. Mould filling numerical methods and algorithms have been recently reviewed by Chen et al.[7]."

Jan 1, 1999

By Nicola Baldo, Marco Pasetto

"The paper discusses the results of a laboratory study, aimed to evaluate the suitability of the bottom ash from Municipal Solid Waste Incineration (MSWI), obtained from different Italian plants, to be recycled in the lithic skeleton of bituminous mixtures, for base layers of road and airport pavements. The research involved a preliminary study of the physical and geotechnical properties of the bottom ash by itself; it was followed by a mechanical characterization of the bituminous concretes. The traditional Marshall methodology was used to identify the optimum bitumen content; the mixtures were also mechanically checked by means of the stiffness modulus test, repeated load axial test and fatigue test. Because the requisites for acceptance in the Italian Specifications and Standards have been satisfied and given the positive mechanical performances, it has been verified that the MSWI bottom ash can be used as substitution of the lithic materials in the road bases, also with very high contents (up to 81% on the weight of the aggregate). Introduction The incineration of Municipal Solid Wastes (MSWs) provides for by-products which can be mainly classified as bottom ash and fly ash. The first one, corresponding to the 25% on the weight of the wastes to be incinerated, so resulting the principal product of the process, is mainly composed by Silica (Si), Iron (Fe), Calcium (Ca), Aluminium (Al), Sodium (Na) and Potassium (K) oxides, so presenting a composition similar to that of different natural materials. Its metallic fraction can be recovered; the remaining part is usually stocked in dumping or, less frequently, recycled. Bottom ash can be re-utilised in the construction of new infrastructures, especially in bitumen bounded mixtures, because of the inert properties of the binder which covers the grains with a subtle film, that prevents the release of heavy metals. The paper describes a study aimed to design new bituminous mixes for flexible road and airport pavements, realised with the highest content of 4 types of bottom ashes, deriving from different MSWI plants of the Northern Italy. The ashes will be named as BA1, BA2, BA3, BA4 respectively (the origin cannot be specified)."

Jan 1, 2008

By Sun-Hee Cheong

This study sought to produce L(+)-calcium lactate using precipitated calcium carbonate as a starter culture composite of lactic acid bacteria in lactic acid fermentation. Specifically, precipitated calcium carbonate was synthesized by reacting calcium hydroxide with sodium carbonate in the previous study by the authors. Synthetic precipitated calcium carbonate was then used as the calcium source of lactic acid bacteria during the fermentation process. In general, precipitated calcium carbonate has low absorption rate in the human body. On the other hand, calcium lactate has high absorption rate; it is commonly used in food and drug industries as calcium additives in various foods such as cookies, beverages, bread, sauces, powdered milk, and fruit juice. Calcium lactate has two racemates, e.g., L(+)-lactate and D(-)-lactate. In particular, L(+)-lactate is known to be more soluble than D(-)-lactate and generally produced from lactose by homo-fermentative lactic acid bacteria such as Lactococcus spp., Lactobacillus plantarum, Lactobacillus casei, Lactobacillus curvatus, and Pediococcus spp. Thus, the characteristics of the pertinent lactic acid bacteria and optimal condition such as temperature, pH, precipitated calcium carbonate addition rate, and content of fermentation for increasing formation yield and purity were investigated. The findings suggested the possibility of manufacturing L(+)-calcium lactate using precipitated calcium carbonate as a calcium source with high value-added instead of commercial calcium lactate.

Jan 1, 2006

By R. Boom, B. Kraaijveld, H. Kuntzel, Y. Meteleva-Fischer

"Alloying refining with rare earth elements followed by acid leaching was examined for the potential of upgrading of metallurgical grade silicon. Microstructure study of silicon alloyed with small additions of rare earths showed behavior relatively similar to the influence of calcium addition. After alloying with neodymium the phosphorus content was detected in various intermetallic silicides containing neodymium and iron. The content of lanthanum and neodymium in refined silicon was by several times lower than that of aluminium and calcium. Alloying with lanthanum and neodymium at smaller additions than calcium reduced the phosphorus content down to the same level. The efficiency of lanthanum and neodymium in removal of boron and phosphorus at the 1-2 wt% of their additions and their low solubility in silicon make the alloying with these metals followed by acid leaching an attractive option for the refining route of metallurgical grade silicon up to solar grade.IntroductionA striving for a cheap ""green"" energy directs the research interests in silicon solar cells towards new efficient refining routes for metallurgical grade silicon (MG-Si, -98% purity). The silicon price determines up to high extent the solar module's price, so that cheap and efficient metallurgical process is awaited. The research challenge is to fulfil the purity requirements of solar grade silicon (SoG-Si, 6N) by competing with the energy-consuming and environmentally unfriendly Siemens process. Most difficult impurities to remove are boron and phosphorus, so technologies dedicated to their efficient removal attract an attention of industry and academia.Alloying refining (also known as solvent refining) is one of the most promising refining options, which is based on a principle of solid-liquid extraction using limited solubility of impurity elements in solid silicon [ 1]. Various elements were proposed for alloying refining: aluminium [2], calcium [3], tin [4], iron [5], copper [6] etc. The attractiveness of the alloying refining is in decreasing a melting point of the metal mixture and an affinity of the alloying element to the most harmful impurities, especially to boron and phosphorus. However, the difficulties are still faced due to self-solubility of the alloying elements, their low affinity to boron and/or phosphorus, silicon losses and necessity of removal of the silicide impurity phases in an additional step, using acid leaching [7], fractional melting [ 8] etc."

Jan 1, 2013

HW Process Technologies, Inc. (HWPT) has developed a patented membrane-based ion fractionation system, which specifically separates copper from gold and silver species in a cyanide matrix. This Engineered Membrane Separation (EMS?) system was pilot demonstrated on the 82,000 liters of pregnant leach solution' (PLS) generated from tailings, via thin layer leaching, at a mine site in Durango State, Mexico. The EMS? recovered ~90% of the gold-silver cyano-complex to a 90% volume permeate (based upon an EMS? feed stream of 100% volume) while rejecting -90% of the copper cyano-complex to a \0% (by volume) concentrate. The EMS? technology combines pore-size specific electro-statically charged membranes with engineered materials of construction and application-specific operational design that reject multi-valent, ionically charged species to the concentrate and transmit mono-valent species through the membrane to the permeate. The 850 ppm Cu PLS contained approximately 0.8 gil free NaCN with, the copper cyano-omplex principally in the CU(CN)3 and CU(CN)4 forms. The gold grade of the PLS was -2 ppm Au. The ~LS calcium concentration at -700 ppm Ca was reduced to ISO ppm.Ca (± 50 ppm) by sodium cycle ion exchange pre-treatrnent prior to EMS? processing.

Jan 1, 1998

By E. Almendras de Siegel

Pyrometallurgical processes have the thermodynamic capability of treating complex and dirty ores and concentrates to produce high purity metals and inert slags. Modem pyrometallurgical processes are environmentally sound and competitive with other processes. However, there is still a need for sensors and other practical tools that permit a rapid evaluation of the performance of these processes. In order to contribute to satisfying this fundamental requirement, the authors developed the IDENT.LA software that permits the automatic mineralogical analyses of inorganic materials, including the final and intermediate products of pyrometallurgical processes. The technique allows determining the grain size distribution of mineralized inclusions, the surface relations between metallic phases, and conducting modal analyses of the essential phases that are present in the samples. Three basic automatic operations are performed: creating a representative image of the sample; identifying the metallic and non-metallic phases; and measuring the features of the resulting image. The results are used to evaluate the performance of pyrometallurgical and other processes. In this paper, the authors discuss the application of the technique to a sample of slag from a slag cleaning process that uses a carbonaceous reductant. In this case, process performance impacts not only on the efficient reduction of the slag magnetite and on copper recovery but also on the quality of the process off-gas. The mineralogical analysis of the slag is a valuable tool in assessing process performance and in recommending changes of operating conditions.

Jan 1, 1999