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By Renato G. Bautista

The chemistry of the separation of metals from each other and from the other undesirable components involve multiple simultaneous chemical reactions. In the case of leaching, the heterogeneous chemical reactions between the solid and the liquid phase may be limited to a few reactions. In the homogeneous liquid phase, the number of simultaneous chemical reactions could be double or triple that of the number of heterogeneous reactions:. The rate of dissolution becomes very dependent on the changing concentrations of the significant chemical species taking part in the multiple reactions in both the heterogenous and homogeneous phase. The rate expression developed for the process must take into account the mechanism of chemical reactions in order to best represent the actual process. This paper also examine the role of mass transfer with chemical reaction in the develpoment of the rate equations for dissolution, liquid-liquid extraction, membrane separation, precipitation, and electrodeposition.

Jan 1, 1996

By Matthias Schnitzler, Herbert Pfeifer, Ralf Bolling

"To transform metals high temperatures are usually needed. A fast and efficient heating can reduce the C02 emitted. The fastest way to heat metals is called direct flame impingement (DFI). The flame impinges upon the item being heated. For this method it is important to know the shape and length of the flame. Laser-induced fluorescence (LIF) technology allows measurements of a two-dimensional field without influencing the reaction or the flow. Commonly used is the measurement of OH-radicals, an indicator of the reaction zone.In the presented study measurements of a turbulent diffusion flame are shown. The position of the reaction zone and the influence of the distance between the item being heated and the burner are investigated. Conventional measurements and LIP-measurements are compared and the potential of DFI to increase the efficiency of heating metals is discussed.IntroductionDuring industrial heating processes a fast and efficient heating technology is required. Two important aspects are the NOx emission and the energy efficiency. The direct flame impingement (DFI) technology has the highest heat transfer rate possible with a gas/air flame. The turbulent high velocity flame jet impinges upon the item being is heated [ 1]. Due to the high heat transfer rate furnace and exhaust gas temperatures are lower. Therefore the energy efficiency is increased and the amount of NOx emitted is reduced.Hydroxyl- (OH-) radicals are an intermediate product that is generated during the combustion of hydrocarbons [2]. They are commonly considered as an indicator for the reaction zone and position of heat release. Figure 1 shows the hydroxyl-mole fraction in dependence of the distance along the gas flow. The figure clearly shows how fast the OH-concentration increases in the reaction zone. Figure 1 also shows that OH-radicals are present in the post combustion region, however in smaller concentration [3].The laser-induced fluorescence technology serves to measure the spatial distribution of OH-radicals in a two dimensional cross-section area of the flame. Therefore the flame dimensions and location can be determined with high spatial resolution without influencing the flow or the reaction [ 4,5]."

Jan 1, 2012

By Sibin Zhang, Shengli Wu, Youhao Yin, Yuandong Pei, Zhixing Zhao, Jiangshan Shi, Zhengyun Fan

Spraying medium to achieve an energy-saving and emission reduction for iron ore sintering has been researched, such as spraying natural gas, coke oven gas, oxygen, sintering flue gas and gas from annular cooler. This paper focuses on effect of spraying steam on sintering surface on reduction of NOx and dioxin emissions in practical sintering production in Shougang Jingtang. It can be found that, with the increase of sintering bed spraying steam amount, NOx and dioxin of flue gas showed a decreasing trend. As spraying steam 1 t/h for 550 m2 sintering machine in Jingtang, NOx content decreases 2.6–9.5 mg/Nm3, and dioxin decreases 0.007–0.014 TEG ng/Nm3.

Mar 1, 2018

By G. Pantazopoulos, A. Vazdirvanidis

In this paper, a failure analysis investigation is presented concerning the intergranular cracking of three different diameter (Ø26.6, Ø10.8, Ø8.5 mm) high strength brass rods which failed after extrusion. Optical, Scanning Electron Microscopy and Electron Backscatter Diffraction are employed in order to reveal the mechanisms and the root causes of the failures. The microstructural characteristics, exhibited by the brass rods, pertaining mainly to phase, grain structure, size and distribution of intermetallic particles, are considered to exert a detrimental effect, impairing the mechanical properties, facilitating the environmentally-induced degradation and assisting the occurrence of brittle fractures. Revision of preheating and extrusion conditions could be further implemented in order to minimize the risk of such failure in the future.

Mar 1, 2018

By Takashi Miyamoto, Hideo Nakae, Hideki Yamaura, Takeshi Yanagihara

"For the production of partially composed metal matrix composites, namely discontinuous MMCs, using a casting· process, the interpenetrated phase composites with SiC particles were fabricated by pressureless iDfiltration using molten Al-Si alloys. This process is based on a wetting phenomenon, therefore, we discussed the technique based on the reactive wetting. The SiC particles coated by diluted water glass were sintered in a mullite Tammann tube and simultaneously infiltrated with molten Al-Si alloys in air at 1173~1573K. As for the improvement of the wettability between the SiC and the liquid aluminum alloy, Fe3O 4 powder was mixed with the water glass due to the thermit reaction between Fe3O4 and molten aluminum alloy. In some experiments, pure aluminum powder was placed on the sintered SiC to increase the interfacial area and the chemical reaction between the sintered Sic. and the melt. By combining these conditions, we succeeded in the complete infiltration without pressure at 1173K.IntroductionAs is well known, the mechanical properties of metal matrix composites (abbreviated MMCs) are superior than that of ordinary metals. However, their use has not been widely accepted because the production cost is very high due to their poor machinability. Therefore, the production of partially composed, namely discontinuous MMCs, by as the Lanxide process [l,2] has been investigated for many years. The Lanxide process, it takes a long time, sometimes up to 10h, in a nitrogen atmosphere for the infiltration. Therefore, the cost will be higher for common use. On the other hand, a high 'pressure process has been adopted for the production of discontinuous MMCs by the Toyota Motor Corp.[3]."

Jan 1, 2000

By Renato G. Bautista

"The chemistry of the separation of metals from each other and from the other undesirable components involve multiple simultaneous chemical reactions. In the case of leaching, the heterogeneous chemical reactions between the solid and the liquid phase may be limited to a few reactions. In the homogeneous liquid phase, the number of simultaneous chemical reactions could be double or triple that of the number of heterogeneous reactions. The rate of dissolution becomes very dependent on the changing concentrations of the significant chemical species taking part in the multiple reactions in both the heterogenous and homogeneous phase. The rate expression developed for the process must take into account the mechanism of chemical reactions in order to best represent the actual process. This paper also examine the role of mass transfer with chemical reaction in the develpoment of the rate equations for dissolution, liquid-liquid extraction, membrane separation, precipitation, and electrodeposition.IntroductionThe understanding and the elucidation of the mechanism of the rate phenomena for a specific chemical reaction system is of prime importance in the development of a successful chemical process. The development of successful emerging technologies for metals separation will depend on the accurate interpretation of the intrinsic chemical reaction kinetics and the rate of mass transfer of the desired metal species during its separation from the undesirable chemical species. This is the case whether the process application is for separation, concentration, and /or purification.The chemical processes that will be examined in this presentation will include leaching, solvent extraction, membrane separation, precipitation, and electrodeposition."

Jan 1, 1996

By Y. Iguchi, T. Narushima, T. Shiozawa, M. Maruyama, R. Arashi

"In situ observation system for thermal oxidation using Raman spectroscopy' was constructed, and oxide films formed on liquid pure Al and Al-Mg alloys (Mg contents = 1 and 4 mass%) were analyzed at room temperature to 1273 K in dry oxygen. In situ Raman spectra of the surface of a liquid Al-:-4mass%Mg indicated the formation of MgO • AlP3 (spinel) as oxidation products, while a -AlP3 and MgO • Alz03 (spinel) were observed on a liquid Al-1mass%Mg alloy. It was suggested that the formation of MgO film affected oxidation behavior of these alloys.IntroductionLiquid aluminum alloys are cast to ingots mainly by the continuous casting process. It is well-.known that surface cracks could be caused by oxide films formed on the surface of melt during continuous casting and defects due to the film. With regard to oxidation behavior of liquid aluminum alloys, many investigations l -s have been carried out from the view point of formation of ceramic metal composites(CMC) which are expected as cutting tools and structural materials 1.2. It is very important for reasonable continuous casting and CMC formation processes to elucidate oxidation behavior of melts.Oxidation behavior of materials generally depends on compositions and properties of oxide films formed on the surface. If in situ observations of oxide films are available during oxidation, evaluation of oxide films and interpretation of oxidation mechanism could be expected. Laser Raman spectroscopy is one of the most appropriate techniques for in situ observation of oxide films under various atmosphere at high temperatures. The authors have discussed the effects of atmospheres and sample compositions on oxide film formation mechanism on Fe-Si alloy6 and SiC-B4C composite7 on basis of an in situ observation by Raman spectroscopy. In spite of many previous studies, systematic and clear explanations have never been gotten on oxidation behavior of liquid aluminum alloys. And no in situ observation has been made except for transmission electron microscopy(TEM) and X-ray diffraction(XRD)."

Jan 1, 1996

By A. J. Paul, K. O. Yu

"Today, foundries are moving towards the use of models and design tools to gain a competitive advantage in producing castings of high desired quality. This leads to a growing alliance between foundries, software developers and researchers seeking to model, visualize and understand the phenomena taking place during the casting process. In addition, there is a need to develop affordable techniques to produce parts in small lot sizes. This leads to the development of a Flexible Manufacturing System consisting of: (1) up-front computer-aided engineering; (2) computer integrated proto typing with solid freeform fabrication; and (3) fabrication of the actual mold and related equipment to cast the part.This paper discusses some of the developments that are taking place today in the areas of modeling the physical phenomena during the casting process as well as towards developing a Flexible Manufacturing System for producing cast parts. Areas that require most work involve prediction of defects and mechanical properties using simplified analyses. In addition, electronic data sharing for collaborative engineering between geographically dispersed team members is also discussed. Case studies are presented showing successes as well as failures.IntroductionCasting, one of the oldest forms of metalworking, has recently seen a flurry of developments in the area of solidification modeling. These developments have come about after the realization that, in order to stay competitive, foundries need to reduce their scrap rate and production costs, and increase casting quality. Even though this is not new knowledge for foundry engineers, the tools to help them achieve this goal are just being developed and put in place for use by foundries. Several state-of-the-art software packages are currently available to analyze the solidification behavior in complex shaped castings. These packages make use of several different approaches for solving the various problems associated with casting processes. The overall architecture of a comprehensive solidification modeling system is shown in Figure 1."

Jan 1, 1994

By Gabriel Riveros, Ariel Balocchi, Andrzej Warczok, Daniel Smith

Blister copper from converting of copper matte is processed by fire refining prior to electrorefining. The fire refining consists of two steps: copper oxidation with impurities slagging and copper reduction. The classical batch process is carried out in vascular or reverberatory furnaces called anode furnaces. A new process for continuous copper fire refining has been proposed. The copper flows through two reactors in cascade, where is oxidized and reduced. The flow of a liquid copper through a ceramic packed bed increases the surface area and the rate of oxidation as well as the rate of reduction in the packed bed of charcoal. Mathematical modelling allowed for the design of a laboratory scale demonstration installation and industrial-pilot installation in Hernan Videla Lira Smelter (Paipote). The results have demonstrated the process feasibility and flexibility in operation.

Jan 1, 2009

By P. N. Anyalebechi

A comparative study of the mechanical properties of automotive steering knuckles produced by three different shape-casting related processes has been conducted. It involved the characterization of the tensile and fatigue properties of aluminum alloy A356 knuckles produced by the vacuum/pressure riserless casting (VRC/PRC), pressure counter pressure casting (PCPC), and the hybrid Cobapress (a casting-forging) processes, in accordance with the appropriate ASTM standards. Surprisingly, the knuckles produced by the hybrid Cobapress process exhibited the lowest strength. For example, the average 0.2% yield strength of the Cobapress knuckles was 31 MPa and 40 MPa less than that of the VRC/PRC and PCPC knuckles, respectively. However, between stresses of 150-200 MPa, the fatigue lives of the VRC/PRC, PCPC, and Cobapress knuckles were comparable. But above 200 MPa, the Cobapress knuckles exhibited the lowest fatigue life. The observed differences in the mechanical properties are attributed to the inherently different microstructures of the different knuckles.

Jan 1, 2009

By M. T. Thomas

Sufficient development of the X-Ray Photoelectron Spectroscopy (XPS), the Auger Electron Spectroscopy (AES), and the Secondary Ion Mass pectroscopy (SIMS) has made these instruments ideal for solving problems related to mineral processing -particularly gold ore processing. XPS can determine both the surface composition and chemistry of ores and tailings, and the various phases within either of them. AES can also determine surface composition with the further advantage of having greater spatial resolution so the surface chemistry associated with specific minerals in the ore can be identified. This identification helps to clarify why some minerals pass through a chemical process unaffected, while others can be successfully treated. SIMS has an elemental sensitivity from one to four orders of magnitude greater than XPS or AES which makes it useful for detecting the presence of some elements in very low concentration (parts per million).

Jan 1, 1981

By Sen-xiang Yang, Xin-teng Liang, Gui-jun Li, Jian-hua Zeng, Yong Chen

"This research is based on PANSTEEL 120t steelmaking converter technology to have the quantitative description of the time needed in uniform mixing of molten steel in the converter with the computer. In present work, the numerical simulation approach is used to analyze oxygen lance nozzle, the flow condition of oxygen and flow status of molten steel in the converter. The various oxygen jet flows that come out from different angles and the flow status of all kinds of jet flows in the converter have also been simulated. All of the simulation parameters are based on the specifically practical conditions according to the physical conditions of PANSTEEL 120 t steelmaking converter. Through numerical simulation, the angle parameter of the oxygen lance nozzle is 16 °. The optimized oxygen lance 536-16 has a good performance in industrial application. This kind of phenomenon shows that the ways and processes of numerical simulation in this research are right.IntroductionThe oxygen lance system is the significant process in semi-steel making converter. It's related to whether the converter or even the whole system can function well. While in actual production, many problems emerge in the process of using the former oxygen lance, such as re-drying, slopping, high lance position, dead burning and even blowing out. In continuous fast-paced process, the unstableness of oxygen lance will lead to speed droop or even stop pouring. Analysis shows that all these problems are not only related to the raw materials but also the design of oxygen lance. Bad oxygen lance's scorification kinetics condition and low content of FeOn in early slag are the direct factors that we cannot easily control in steelmaking at present [l]. Therefore, the good scorification kinetics condition which is related to nozzle has good influence on BOF steel making."

Jan 1, 2013

By Ahmet Haxhiaj, Jaroslaw Drelich

"Both composition and porosity of pellets are the main parameters influencing the reductive melting process in water-jacket furnace during the roasting of sulfide lead concentrate. Roasting in a smelter located in Trepçë is done at about 9000C, for pellets which are composed of PbS, CaCO3, Fe2O3, and SiO2. In order to faciltiate the formation of slag in the reductive melting, the pellets must have the proper content of CaO, SiO2, and FeO, and porosity. The plant’s practice indicates that pellets with porosity of 18% do not melt adequately in the water-jacket furnace. The optimum porosity for the proper melting of pellets needs to be 32-40% and can be achieved when pellets are loaded with more than 10 wt.% CaO. Pellets with less than 10% CaO have a limited network of pores, such that reactive gases cannot reach the entire ore structure. Also, the composition of the pellets must satisfy the ratio of CaO : SiO2 : FeO = 1 : 1.2 : 1.8 to facilitate the formation of slag in the reductive melting process.IntroductionAgglomeration roasting of sulfide lead concentrate is an important phase in the production of lead by reductive melting [1-6]. The reductive melting process is a complex process with contradictory effects of several technological indexes which many times are hard to measure and determine. In this process, loading the water-jacket furnace with pellets of optimized composition and structure can reduce the consumption of coke, and achieve high level of lead recovery. Pellets (agglomerates) should be porous, but at the same time they should have necessary mechanical strength. ‘Self-melting’ ability of pellets is controlled by the types and quantities of fluxes blended into the pellet composition. Three major additives and their role are:"

Jan 1, 2011

By Henrique Kahn

The Anitapolis alkaline massif in southern Brazil underlies a sub circular area of 6 km2. Bore-hole data show a concentric rock distribution, with mafic rocks in the central part and felsic rocks in the border zone. The rocks are covered by talus and weathered material, 30 m thick on average, and very inhomogeneous in composition. Phosphate mineralization associated mainly with two levels of the weathering mantle and with fresh rocks. A preliminary ore-type classification was based on distribution of apatite, feldspar, vermiculite, biotite-phiogopite, calcite, pyroxene, amphibole and analcime, determined by semiquantitative diffraction method. Technological tests performed on eluvial ore samples from three adits resulted in a subdivision of ore-types based on the difference in behavior due to mineral characteristics during mineral pr

Jan 1, 1991

By F. J. J. van Loo, A. A. Kodentsov, J. A. van Beek, M. R. Rijnders

"A periodic layered morphology of the reaction zone has been observed in several annealed solid/solid diffusion couples, including metal/metal and metal/ceramic couples. This morphology is characterized by a regular array of alternating layers, which are either single-phase layers or bands of particles embedded in an intermetallic matrix phase. A description of several systems showing periodic layer formation is given. It is shown that the periodic layered structure with the single phase layers and the one with the bands of particles have a different mechanism of formation.IntroductionSolid state reactions in ternary systems can produce a variety of reaction zone morphologies if there are two or more reaction products. Three types of morphology have been described in detail: 1) simple layered; 2) isolated precipitates in a singlephase layer; 3) interpenetrating columnar (lamellar) or interwoven structure. Understanding the factors that govern the formation of different morphologies is of importance in many fields of engineering. For solid state displacement reactions the conditions governing the formation of these morphologies are well understood [1-4]. For example, the development of a layered or aggregate reaction zone depends on the relative diffusivities of the components through the reaction products.This paper is concerned with the periodic layered morphology which has been observed in various solid state systems. We consider this to be a fourth type of reaction layer morphology. Two manifestations of periodic layered morphology may be distinguished. One form consists of regularly spaced layers of particles of one reaction product embedded in a matrix phase (another reaction product). The other form consists of single-phase layers embedded in a matrix phase. It will be shown that each manifestation has its own mechanism of formation. In section A we consider a system (Ag/Ti-foil/Si) in which periodic layer formation will be explained as a special case of the Liesegang phenomenon. In section B we consider systems where the periodic layered structure has a different origin."

Jan 1, 1996

By Germán Richter a

To comply with the chilean air quality regulation requirements, the Hernan Videla Lira Smelter which is a custom smelter having to cope with a wide variety of concentrates, has developed a two-step modernization plan. The main steps are: - A second acid plant of 80,000 Nm3/hr to be operating at the end of 1996. This will increase the sulphur capture from 43% to 701/o in association with the replacement of the Hoboken converter by a second PS-converter to reduce the operation problems resulting from the treating of high garde matte. - Oxygen enrichment, is going to be incorporated in 1998 in the Teniente Converter and PS-converters in association with tuyere injection of dry concentrates, increasing the sulphur capture to 90 - 93% of sulphur inputs. By this program, sulphur emissions will be decreased from 40,000 tpy today to less than 8,000 tpy and in this way to carry out the environmental regulations.

Jan 1, 1996

By J. W. Matousek

Copper losses in smelter slags are :typically normalized with some form of the distribution coefficient, written as the ratio of the weight percent assays of metal in slag to the metal in matte or its inverse: L(s/m) = %(Cu)/%[Cu] or L(m/s) = %[Cu]/%(Cu) However, this simple approach ignores the dynamics of the smelting process. It overlooks the effect of the chemical work done in producing a given matte grade from concentrates of different grades -- or from a single concentrate blended with varying quantities of copper bearing precipitates or reverts. This paper examines the combined influences of matte grade and the work done in smelting on the copper content of smelting furnace slags. A simple model for the relationship is proposed.

Jan 1, 1999

By B. L. Chulu

In the carbothermic reduction of lead sulfate to produce lead, the inclusion of soda ash (Na,CO,) in the charge provides for the control of sulfur dioxide in the effluent gas. An important mechanism in the process appears to be the carbothermic reduction of the sodium carbonate whereby sodium gas and carbon monoxide are produced. These intermediates then participate in the reduction of the lead sulfate to produce lead metal and stable sulfur species in the molten slag phase. In addition, there is some evidence that the presence of lead metal in the charge may also serve to increase the lead recovery in the process. These aspects were investigated by conducting laboratory-scale smelting tests with small charges (;3g), at 1173°K(9000C). Recovery did not exceed 74w% and the role of incipient lead metal in the charge could not be clearly assessed.

Jan 1, 1993

By R. J. Wesely

In recent years the trend in copper smelting has been to expand existing smelters to increase their throughput. New smelters under consideration are large, typically in excess of 200,000 tons per year of copper. Despite this trend to larger smelters there are a number of conditions where a much smaller smelter can be economically viable. This paper examines these conditions and outlines the process concepts for a small smelter treating from 20,000 to 100,000 tons per year of copper.

Jan 1, 2000

The kinetics of the oxidation of cyanide by manganese dioxide was studied using a rotation disc electrode system. The rate? of the half-cell reaction of cyanide oxidation is increased at higher hydroxide concentrations. An addition of copper up to 0.001 mole/l was found to enhance the diffusion current, especially at a high hydroxide concentration (0. 1M). A similar enhancement of the reaction rate is also achieved with nickel added at levels up to 0.01 mole/l. Manganese dioxide however requires a i:ow pH to achieve reasonable reduction rates. Leaching studies indicated that the initial reaction rate is strongly dependent on pH, initial concentration of cyanide. Using manganese dioxide cyanide could be oxidized at neutral pH's and ambient temperatures.

Jan 1, 1989