Search Documents

By Aline Maria dos Santos Teixeira, Francisco Manoel dos Santos Garrido, Joao Alves Sampaio, Marta Eloisa Medeiros

"Rocks for crops is a natural practice for soils fertilization which consists on adding rocks to the soil while water decomposes the rock, through chemical weathering, and gradually releases nutrients to the soil solution. This practice can be considered an alternative to the low production of potassium fertilizers in Brazil. In this context, the phonolite rock was characterized in order to evaluate its application as an alternative source of nutrients to the Brazilian agriculture. The phonolite studied is an igneous, volcanic rock with alkaline character that is chemically composed of a high grade of potassium due to the presence of feldspar minerals. In order to quantify the minerals present in the sample, characterization was carried out using several techniques such as X-ray diffraction, X-ray fluorescence and scanning electron microscopy.IntroductionBrazilian soils are generally acidic and nutrient poor due to the tropical climate in which high temperatures and intense rainfall favor a rapid decomposition of the rocks that from the soil. And as agriculture is one of the main bases of the country's economy, large amounts of fertilizer are used to make the soil productive.Although Brazil has large reserves of potassium, the demand for potash fertilizer is higher than the national supply, which makes the country dependent on fertilizer imports, especially in the form of potassium chloride. Thus, we must look for economic alternatives to traditional fertilizer [1].Stonemeal is a natural practice for soil fertilization that consists in adding basic or ultrabasic rocks to the soil so that water, through chemical weathering, decomposes the rock while it gradually releases nutrients."

Jan 1, 2011

By R. C. Hubli

Copper (II) chloride has proven to be an efficient lixiviant for copper sulphide ores and secondary sources of copper such as scrap. Nickel sulphides are generally associated with copper ores and copper-nickel matte is an intermediate product of processing mixed sulphides. While the copper species in aqueous chloride media are present as chlorocomplexes, the presence of nickel as Ni++ offers effective separation between the two by solvent extraction techniques. Oxidation of millerite by cupric chloride in sodium chloride solutions has been studied as a function of rate of agitation, leaching time, temperature, acid concentration and total initial cupric concentration. The reaction has a 1/2 order of dependence on initial cupric concentration in the range of 0.0 to 0.5M. The activation energy for the temperature range 333 -363 K has been found to be 59.2 kJ/mol with chemical reaction at the unreacted mineral surface as the rate controlling step. The rate expression, according to the shrinking-core model, for initial cupric concentrations between 0.0 to O.5M, is evaluated as

Jan 1, 1996

By L. Béjar-Gómez

The aim of this research work is to study and characterize precipitates in structural microalloyed steel by transmission electron microscopy and analysis by high resolution (HRTEM). Microalloyed steel with titanium was produced by casting in an electrical induction oven of 25 Kg. capacity. Carbon content in steel was less than 0.1 % and titanium content of 0.04%. Steel was processed thermomechanically; reheated to 1250ºC and hot rolled on a laboratory mill to a 13.0 mm thick plate with a finish rolling temperature of 900ºC and thickness reduction of 80%. Analysis by High Resolution Transmission Electron Microscopy (HRTEM) identified precipitates in the steel; type and morphology. Energy Dispersive Spectroscopy (EDS) analysis was applied to obtain the chemical composition of precipitates and the matrix. STEM-EDS analysis was also applied to obtain the element profile of precipitates. The results showed the presence of carbonitride precipitates of titanium, Ti (CN), with a circular morphology and size of 10 nm and less.

Jan 1, 2006

By W. C. Chang

Phases and magnetic evolutions of melt spun Nd9.5(Fe1-xCox)85.5B5 (x=0, 0.05, 0.1 and 0.15), (Nd1-yLay)9.5Fe85.5B5 (y=0, 0.0.5, 0.1; and 0.15) and (Nd0.95La0.05)9.5(Fe1-zCrz)81.5B9 (z=0, 0.033, 0.067 and 0.1) nanocomposites: have been investigated. It was found that a. dilute Co substitution for Fe, x=0:05-0:15, in Nd9.5(Fe1-xCox) 85.5B5 improved not only Curie temperature but also the remanence and maximum energy product. Partial substitution of La for Nd in(Nd1-yLay)9.5Fe85.5B5 may suppress the grain growth of the materials during thermal treatment. Exchange coupling between the Nd2Fe14B and a-Fe was found: to increase with increasing La content. A dilute La-substitution, y=O. 10, has proven to decrease the optimum wheel speed required for preparing melt spun ribbons with better magnetic properties; Furthermore; a slight substitution of La for Nd in (Nd0.95La0.05)9.5(Fe1-xCrx)81.5B9 nanocomposite reduced the crystallization temperature of the over-quenched ribbons and led to the formation of a multiple phases mixture. Nevertheless, a dilute Cr addition increases the Tg of (Nd0.95La0.05)9.5(Fe1zCrz)81.5B9 and also suppresses the formation of the undesired (Nd,La)2Fe23B3 and Fe3B phases: Cr was found to play an important role in grain smoothening or magnetic separation which consequently increased the Hc of Cr-containing materials.

Jan 1, 1997

By José Roberto de Oliveira

Based on literature review one can see that the main objectives of MnO reduction is the comprehension of slag interactions and reactions with other elements beyond carbon. That's because it is worthwhile to study pure MnO reduction, where there will be not oxides interaction and just carbon will be the reduction agent. By a thermodynamic analysis we know that Si can react with MnO, then it's important to study this influence, so as Mn content. Our work aims to develop kinetics parameters for the MnO reduction, varying Mn and Si contents in bath. This has been given by pressure measure of CO in a Fe-C bath. The CO is generated by the oxide reduction with carbon. It has been proved that: - Mn content decreases the MnO reduction; - the MnO reduction is mainly influenced by Si content in a bath containing Iron, Carbon and Manganese so as Silicium

Jan 1, 1997

By O. A. Bascur

Applying the latest information technologies in mining and metallurgical complexes has become a serious challenge to management and technical teams. Emerging component design is changing the way the user relates to the desktop. Connectivity between mining and metallurgical process operations and their business systems has become a reality. Expanded use of plant information on the desktop is a standard tool for revenue improvement, cost reduction and adherence to production constraints. The industrial component desktop support access to information for continuous improvement and innovation by staff personnel and engineers. Collaboration between groups enables the implementation of an overall process effectiveness index based on losses due to equipment availability, production recovery and quality rate. The integration of information from mining, mineral processing and metallurgical performance monitoring increases production efficiency, even when many elements cannot be measured directly. Three case studies of large mining/metallurgical complexes are highlighted.

Jan 1, 1999

At the present time, cyanide is the most widely used reagent to extract gold from its ores and concentrates. However, its use in mining has become the focus of intense attack by various groups throughout the world; as a consequence, a renewed effort has been launched to find suitable alternative lixiviants to recover gold. Chlorination was the most popular process to extract gold, before it was rendered obsolete with the advent of the cyanidation process at the turn of the last century, not least because it required the use of potentially hazardous and costly chlorine to oxidize/complex the gold. The PLASTOL® process, originally designed to recover the platinum group metals (PGM?s) from their ores and concentrates, provides an alternative to cyanide for gold ores. The process generates oxidizing conditions in the autoclave capable of forming the AuIII ion, and gold chloro-complexes result from the addition of small quantities (~5-10 g/L) of sodium chloride to the autoclave. The principles of the PLASTOL® process are briefly described, and several applications of the process to gold concentrates are presented. Various options available to recover gold from PLASTOL® leach solutions are also discussed.

Jan 1, 2003

By Kazuyo Yokoyama

New environmental assessment model based on the Waste Input-Output analysis has been developed and applied for the "Landfill mining activity". "Landfill mining" implies the digging up of the landfilled wastes, the recovery of valuable material and energy resources and, thus, the reuse of the saved space as a new landfill site. In this study, the landfilled wastes are assumed to be treated by the gasification/melting processes. Two kinds of reactors, the fluidized bed type (FB) and the shaft furnace type (SF), have been considered in this work as the typical gasification/melting processes adopted in Japan. In FB, the dug-up wastes are heated in the sand fluidized bed zone under reducing atmosphere, Fe and Al are recovered in the metallic form, and then, the gasification/melting of residues is made in the second zone. In SF, the waste is charged in the high temperature coke bed, and the gas is recovered together with molten metal and slag. Both processes generate electric power by the recovered heat and fly ash as waste to landfill. It has been found in this study that the both processes can reduce the total volume of waste and save the available landfill space. SF seems to have higher potential for decreasing volume of wastes because of less emission than FB while FB has great benefit to recover metallic Fe and Al individually. The results of scenario analysis have also indicated that the landfill mining activity is effective for sustainable management of landfill sites.

Jan 1, 2006

By Y. Fautrelle, F. Felten, O. Metais, Y. Du Terrail

"We deal with the prediction of electromagnetically-driven turbulent flows by means of a Large-Eddy- Simulation method (LES). The model is applied in the case of a liquid metal pool submitted to a polyphase linear electromagnetic stirrer. We investigate two cases: (i) the frequency of the magnetic field is equal to 50 Hz; in that case the effects of the pulsating part of the Lorentz forces may be neglected; (ii) the frequency of the magnetic field is low (f= 1 Hz), then the oscillating part of the electromagnetic forces is taken into account. The LES predictions agree well with the mean velocity measurements, as does the standard k-a model. However, as for the turbulent kinetic energy predictions, there is a large discrepancy between the two models. When the oscillating part of the Lorentz forces is taken into account, the computations show that the fluid flow is sensitive to the unsteady part of the forces. We find that the mean velocity is not affected by the fluctuating component of the force. As for the turbulence parameters, the presence of the pulsating part leads to a significant reduction of the turbulent kinetic energy, whilst the turbulence length scale decreases.IntroductionElectromagnetic stirring is commonly used in various metallurgical processes. In continuous casting for example, it may improve the structure of the solidified metal products. Fluid flows generated by electromagnetic stirrers have been extensively investigated (1 ). As for numerical predictions, many works have been published on the subject. In most of the previous works, onepoint closure models have been used. The most used model is the well-known k-i:: model. Those models yield fairly good results as for the mean velocity prediction. However, it has two main drawbacks:(i) the turbulence is not predicted accurately,(ii) it is not well fitted for unstationary flows as well as transitional turbulent motions, where theReynolds number is moderate."

Jan 1, 1999

By Kohei Yajima

The dusts and fly ash generated from the steelmaking processes and municipal solid waste incineration processes contain metallic elements such as Fe, Zn, Pb and Cd with considerable amount of halogens. In Japan, zinc in dusts is recovered by Waelz kiln or MF process, etc. However, the presence of halogen in the dust affects the evaporation and condensation behavior of zinc and other metals, and disturbs the direct recycling of dust to steelmaking processes, because alkali or heavy metals reacted with halogen vaporize easily as halides and/or oxyhalide compounds in pyrometallurgical process. Recently, the formation mechanism of zinc oxychloride vapor was investigated and the formation of zinc oxychloride such as ZnOCl was proposed. However, considering the practical operation, the effect of water vapor on the evaporation behavior of oxychloride is not fully clarified yet. This study is focused on the investigation of evaporation behavior of ZnO with Ar- O2-HCl-H2O atmosphere.

Jan 1, 2008

By Pradip

The selective adsorption of chemisorbing fatty acids at high temperatures together with the addition of soda ash and lignin sulfonate as depressants is the key to the industrial processing of bastnaesite ores. This paper presents the results of a fundamental investigation that indicate that alkyl hydroxamates can be an alternative collector for the beneficiation of bastnaesite ores that contain barite and calcite as the principal gangue minerals. The primary mechanism for providing sites for the chemisorption of hydroxamate on bastnaesite appears to be through dissolution of cations, formation of the respective hydroxo complexes and readsorption at the interface.

Jan 1, 1989

By Du Sichen

The present paper presents the modeling of gas-solid reactions in the case of the decomposition of CaCO3, describing the reaction kinetics on the basis of heat-transfer concepts which could be compared with thermogravimetric results. In the case of solid-solid reactions, the present paper describes the model developed for describing solid-solid reactions from dynamic X-ray diffraction technique, developed by the present team. The model has been successful in explaining the formation of spinel from MgO and Al2O3.

Jan 1, 2006

By Paul Pajunen, Michael Sheedy

"Acid separation using short bed ion exchange is a now well established technology in copper refinery tankhouses. Refinery bleed streams from liberator cells are treated by short bed systems to produce an acid-free byproduct stream that contains the bleed metals and valuable nickel salts. Removing the acid eliminates the need for a black acid evaporator and reduces the amount of sodium carbonate required in nickel selective precipitation processes. The recovered sulfuric acid can be recycled to the tankhouse. This same technology is routinely used to treat other acids such as hydrochloric, nitric, and hydrofluoric. In the case of hydrochloric acid, the process can selectively separate chloro-anionic complexes such as Zn, Pb, and Cu, which are then eluted with water. The acid recovery technology can also be closely coupled with ion exchange processes in order to minimize regenerant acid consumption. In many hydrometallurgical applications resin regeneration often requires an acid dosage multiple times the stoichiometric minimum. Coupling an acid recovery bed with the IX column allows recovery and recycle of the free acid in the spent regenerant, thus reducing the overall acid consumption to just slightly more than stoichiometric.Short Bed Ion ExchangeThe short bed ion exchange process has been extensively used in the metal finishing industries since the early 1970s [1,2]. Short bed systems have also been sold to primary metals producers for the separation of sulfuric acid from copper refinery bleed streams [3] and for the recovery of nickel and cobalt from plant effluent streams. This unique technology optimizes the ion exchange process and offers a number of significant advantages over conventional ion exchange. The principal features and benefits of this technology are presented below."

Jan 1, 2012

By A. K. Riihimäki

The description deals with duplex stainless cast steels and austenitic high molybdenum steels used in pumps for severe condition service. The main modem nitrogen alloyed duplex cast steels are presented in the ASTM standard A-890. Two grades of high molybdenum austenitic stainless steels there are presented in ASTM A-744 (-96) standard i.e. CN-3MN and CK-3MCuN. The latest and most corrosion- resistant stainless steel grade is AVESTA 654 SMO?. Avesta Sheffield the trademark owner has granted Ahlstrom Pumps license to produce the material. This new stainless steel as pump material for severe service has improved properties in the hydrometallurgy and electrorefining processes of metal and especially in the copper industry compared to duplex stainless steels. The paper deals briefly with the foundry process to manufacture high alloy stainless steel pump castings. The AOD-method (AOD= Argon Oxygen Decarburization) is an important prerequisite for the melting of low carbon, high chromium and molybdenum alloyed nitrogen steels. The properties of these steels are included. The main topic is the corrosion resistance of the above-mentioned pump materials in severe service. Results of short-time erosion and corrosion tests are discussed and compared with the results of plant tests. Practical results of pump materials performance in severe service for the copper industry are given. The new high alloyed cast stainless steel (main elements; Cr-24%, Ni-22%, Mo-7,3% and N-0,5%) has shown improved corrosion and erosion properties as process pump material in several severe service applications e.g. in the metal industry.

Jan 1, 1999

By S. Moussa

The formation of boron-doped nickel aluminides Ni3AI, (76 at. % Ni) from elemental powders by reaction synthesis using reactive sintering was studied. The process involves the mixing of elemental powders of nickel and aluminium with various wt % of boron up to 1 wt % boron. Nickel and Aluminium powders were mixed in the correct proportion to form the intended boron-doped nickel aluminide intermetallic. XRD, SEMI EDS, Image analysis and Archimedes principle; were used to study the effect of Boron addition on the final microstructure, bulk density, average grain size of as reactively-sintered nickel aluminides (boron-doped), compared with no boron addition. The results showed that at greater boron content than 0.3 wt %, a two-phase non-equilibrium microstructure of consisting of NiAI phase in NiJAI matrix was formed that have been primarily retained even after heat treatment for 5 hours at 1000 °C. Boron was present in solid-solution within both the NiAI and the Ni3AI (in greater amounts) phases.

Jan 1, 2001

By Peter Kettle

This paper describes the performance of the copper industry over a period of some two decades and examines the theme that improvements in operating efficiency have not been matched by improved returns on capital. The financial performance of the copper industry is analysed using CRU's MICA database. Regression analysis indicates a two percentage point increase in operating margins but no increase in returns on capital. The gain in operating efficiency appears to have been mainly achieved in the mid 1980s. The investment boom of recent years has resulted in a rapid increase in the industry's level of debt and gearing ratio (now some 47%). Data on 44 copper mine projects is used to show the linear relationship between scale and capital costs. Typically new capacity costs some US$5,000 /tpy. The relationship between cash costs and capital intensity of projects is also plotted. The greater attention now being focused on efficient use of capital means that capital intensity rankings will become increasingly important in determining which projects go ahead.

Jan 1, 1999

By Richard LeSar

Sustainability requires more from engineering than the development of technology. Engineering must also take into account the effects of that technology on the integrated social, economic, and environmental processes that constitute our society. Schumacher introduced the powerful concept of an appropriate technology, by which he meant a technology that is appropriate to the environmental, educational, cultural, and economic situation for which it is intended. While the principles of appropriate technology have been most commonly applied in the developing world, they are equally valid in the developed world as well. In this paper we will review appropriate technology and discuss its role in helping to define a way to think about this broad view of sustainable engineering. We will end by presenting one strategy for introducing the concepts and applications of appropriate technology in an engineering curriculum.

Jan 1, 2010

By Luiz R. P. De Andrade Lima

This paper presents a mathematical model for the oxide copper ore heap leaching process. The data used in the model include physical-chemical, .geometrical and operational data, as: leachable metals ore contents, .flow rate and acid concentration, parameters of passivity, ore size distribution, the average residence time of the solution in the heap, height, irrigated area and weight of ore in the heap. In this model the heap is divided into horizontal and plane layers of constant area. The flow of the liquid in the heap is considered unidirectional and the solid-fluid reaction model is considered under diffusive control. The average residence time of the solution into the heap and the apparent effective diffusivity of the acid through the ore particles have .a significant influence on the rate of the copper extraction and its concentration in the pregnant solution; therefore these parameters are used in the model calibration. When this algorithm was applied to a laboratory test, the results showed that the model is adequate to predict the process performance.

Jan 1, 1999

By Jonathan M. Berkoe

Design engineers and metallurgists have long recognized the need for better methods to calculate a wide range of fluid dynamic effects in smelters and hydro- metallurgical facilities. Examples can range from the capture of fume in the secondary hoods of a copper converter, to controlling the thermal effects of heat transfer resulting from metal and slag flows within a furnace. With the advent of relatively low-cost, high- speed computers and user-friendly, commercially available computerized fluid dynamic (CFD) programs, these calculations can now be made. Use of CFD increased the understanding of both hot gas and molten flows in smelter facilities and has already led to design improvements in converter fume control hoods as well as improved management of heat transfer in electric furnaces. This paper will present two representative CFD applications to metals industry facilities. To date, Bechtel has implemented CFD results on four continents.

Jan 1, 1999

By Ho-Sang Sohn

Copper concentrate particles of 200 to 300 mesh size were fed from the top of vertical reaction tube of 2.8 cm ID and 2 m long with an O2-N2 gas mixture. The reaction tube was heated to 900 K to 1100 K. The residence time of the particles in the reaction tube was about 1 second. The copper concentrate particles were very rapidly oxidized and melted down during their descent in the reaction tube. The particle temperature were calculated by combining an un-reacted core model, mass transfer between gas and particles, and heat transfer between gas, particles and tube wall. The particle temperature reached its maximum within a distance of 60 cm from the top of reaction tube, and it attained at 2000 K at higher oxygen partial pressure. The most particles were melted at the oxygen partial pressure above 20 kPa. An appreciable amount of As, Sb and Pb in the concentrate particles was eliminated in the upper portion of the reaction tube and the rate of elimination are explained by the rate of mass transfer of volatilized species through the gas film on the particle surface and the variation of particle temperature during the descent.

Jan 1, 2006