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By Gerald M. Ellis

Exploration for gold .deposits on Hispaniola has taken place sporadically over the years but has expanded in the past decade. There are veintype, disseminated, alluvial and elluvial deposits. Investigations were previously undertaken in Haiti by combined Haitian, Bureau of Mines, and UN geological teams at Grand Bois Limbe(Milot) and Cap Coq areas. Later studies were conducted at the Miches and Moncion districts. Gold occurrences were reported in quartz, silicic-barite veins and gossans. An important deposit ?at Pueblo Viejo is? a disseminated type where extraction is taking place in the oxidized zone. Exploration by Japanese and West German firms with local geologists are described in this paper together with Pueblo Viejo, Miches, Restauracion, Milot, and Meme ?areas where occurrences are known. Copper deposits with associated gold va1ues are also described. These include vein deposits in Central Cordillera and disseminated deposits at Terrier Rouge and Blondin.

Jan 1, 1989

By James A. Warren

The phase field method has been successfully employed as both a tool to model heterogeneous materials and as numerical method for calculating the motion of interfaces and phase boundaries without explicitly tracking those interfaces. The method has been used to model a diverse suite of problems describing the microstructural evolution in materials. These models are derived from thermodynamic arguments and symmetry principles, and usually guarantee positive local entropy production for systems out of equilibrium. Descriptions of how phase field methods can be applied to the problems of solidification, grain growth, and electroplating will be presented.

Jan 1, 2001

By S. Ikenobu

This paper describes a method for processing high-silicate zinc concentrates by hydrometallurgical zinc refining. Silica in concentrates reacts to form zinc silicate during roasting. The zinc silicate readily dissolves and slowly precipitates in sulfuric acid solutions during leaching. However, if proper operating parameters are not maintained, the colloidal silica may form an unfilterable gel. That is, according to the investigation results obtained, the silica concentration in the reactor has to be maintained at 5 g/1 or less (preferably 2 g/1 or less) by promoting the precipitation reaction. The proposed method has made it possible to precipitate silica in a form having excellent solid-liquid separation characteristics, without the need for facilities having a high filtration capacity, and to maintain a low silica concentration in the reactor by feeding a composition containing pre-adjusted silica contents.

Jan 1, 2000

By V. Tsukerman, Ivanovam L.

"The potential of hydrocarbon resources in the Arctic oil and gas provinces is enormous. Oil, gas and condensate constitute the basis of mineral resource base of the shelf zone of the Russian Arctic; summary volume of hydrocarbons exceeds 100 billion tons of conventional fuel. Only in the Shtockman gas condensate field in the Barents Sea explored balance reserves equal to 3.2 trillion m3 of gas. It is necessary to establish a special regime of nature management in the Arctic. Environmentally oriented economic activities should be more actively stimulated. The Energy Strategy plans that starting from 2010 in the Barents and Pechora Seas up to 10 million tons of oil and 50 billion m3 of gas will be extracted, reaching the level of 30 million tons of oil and 130 billion m3 of gas in 2020. This task cannot be solved without intensification of geological exploration on the continental shelf. IntroductionThe elaborated strategy of mining enterprises should correspond to the modern paradigm of mining industry development which is not only for extraction of minerals but also for multi-profile structure having comprehensive use of the resources on the rational basis intended for rational complex utilization of mineral resources of the Arctic zone of Russia which by the definition includes maximally full use of the whole aggregate of resources on the economically rational basis with obligatory environmental with resource reproductive and socio-economic functions and deterrents"

Jan 1, 2008

By Laurentiu Nastac

"An advanced casting simulation-based optimization approach was applied in this study to assist in the improvement of the mold design of aerospace components made of A3 56 alloy. By using this approach, mold filling and solidification related defects (including macro-shrinkage and shrinkage porosity) were significantly minimized and hence it helped in cost reduction, performance enhancement and quality assurance of complex A3 56 cast parts.An experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and shrinkage porosities were performed using A3 5 6 plates cast in fiiran-silica sand molds using the Prometal's Rapid Casting Technology (RCT) - mold printing technology. Correlations between Niyama values and the pore percentage were also developed. Thus, the severity level of shrinkage porosity can be determined via the Niyama criterion. Predictions were then compared with the macro-shrinkage and porosity measurements in plates of various plate thicknesses and in other commercial A3 56 casting components.IntroductionThis paper describes the process modeling approach used in the development of the mold design technology used to produce assist in the improvement of the mold design of aerospace components made of A356 alloy. Nova Flow&Solid™ software [3] was applied in this study. This casting simulation software was previously validated for several alloys including Ti, steel and superalloys [1-4]. The objective of this paper is to calibrate and validate the simulation software for A356 alloy sand mold castings. For this purpose, an experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and microshrinkage (e.g., shrinkage porosities) were performed using A356 plates cast in fiiran-silica sand molds using the Prometal Rapid Casting Technology (RCT) mold printing technology. The details of the RCT technology are shown in Fig. 1 [5]. Prometal's RCT technology is used for rapid production of sand molds and cores directly from CAD files. The RCT technology relies upon ink jet printer technology to selectively bind the grains of sand to create three-dimensional sand molds and cores. Mold filling and solidification modeling as well as stress analysis are typically performed to properly design the casting and the rig system of each prototype component."

Jan 1, 2012

By A. V. Tarasov

One or more of the main alloying metals, i.e. copper, silicon, nickel, magnesium, zinc and other metals can form a composition with aluminum, by dissolving in the latter. The thermodynamic computations have indicated that within a range of temperatures from 700°C to 1300°C the reactions of molten aluminum with zinc and nickel oxides are shifted toward formation of free metals because it is possible to use the main alloying metals, i.e. zinc and nickel, in the form of inexpensive intermediate products and waste. The laboratory studies conducted have confirmed a possibility for production of aluminum alloys using intermediate products in the form of oxides of alloying metals.

Jan 1, 2006

By Adam Gesing, Ron Dalton, Richard Wolanski, Larry Berry, Christopher Stewart

As the quantity of aluminum recovered from shredder scrap continues to increase, together with increased content of aluminum in automobiles, so does the economic incentive to further upgrade shredder scrap. This upgrade will be done by sorting and recovering the aluminum by specific usable alloy compositions. The metal recycling industry infrastructure needed to deal with the increased aluminum scrap supply already exists. It is an inverted pyramid structure that in North America comprises: 3000 scrap collection yards, 200 shredders, a dozen sink-float plants and one heavy metal sorting operation. The technology for upgrading aluminum sorted from shredder scrap is already either in industrial use or in the final stages of pilot plant development. However, the current automotive aluminum recycling infrastructure will need to adjust to deal with higher volumes of the metal from aluminum-intensive vehicles that will be appearing in shredder scrap -20 years from now.

Jan 1, 2000

By Zhigan Deng

Ni–Mo ore is a black shale containing amorphous colloidal sulfides which have highly active. The oxygen pressure leaching behavior of nickel from black shale in aqueous media is presented. The effects of agitation speed, temperature, oxygen partial pressure and particle size on the rate of nickel leaching were determined. The results indicate that at low temperature hydrothermal and excess oxygen presence, the amorphous sulfides are easily oxidized to sulfuric acid and sulfate, and leaching nickel. The mathematical analyses of the experimental data for various experimental conditions indicated that the dissolution process was controlled by the chemical reaction during the early stage of dissolution, and was then controlled by liquid-film diffusion. In the initial stage of leaching, the reaction depends on oxygen partial pressure.

By Tam Tran

Most new gold mines in Australia are required to treat tailings to reduce cyanide levels before they are discharged to storage ponds to meet the stringent environmental management guidelines set by government statutory authorities. In New South Wales, the average level of weak acid dissociable cyanide allowed in open tailings dams is now limited to 20 ppm, As stringent environmental guidelines continue to be enforced in Australia as well as in other parts of the world, the management of cyanide wastes has emerged as a key issue for the gold mining industry. This paper provides a critical evaluation on technical aspects related to the use of ion exchange resins and affiliated processes in cyanide management and tailing treatment. Particular attention is given to the use of ion exchange resin technologies in the processing of mixed gold-copper ores, where cyanide usage is the highest. Information presented in this paper is heavily drawn from the experience on the application of ion exchange resin processes at May Day mine, in New South Wales, Australia and associated pilot plant test programs. Issues related to the management of thiocyanate, especially with respect to the recovery of cyanide from thiocyanate are also discussed.

Jan 1, 1998

By John Norton

"This presentation will cover the physical properties of waste heat recovery. It is a two part presentation. The first deals with actually recovering the heat with new state of the art heat exchangers and applying that heat to the furnace combustion and the second part will cover what other processes you can enhance with this ""free"" heat. It will also talk about converting it to steam, hot air or electricity to be used or sold back to the utility company. The economics of various schemes will be reviewed. A brief discussion on State and Federal grants and subsidies will be presented.IntroductionThere are large quantities of wasted heat in the usual aluminum melting process. And, there are several techniques for reducing and/or using some of that wasted heat as you have seen. Any technique that can make use of wasted heat is a form of recovery. This can range from simply preheating aluminum billets prior to melting, to more complicated processes like air-to-air heat exchangers using the boiling and condensing characteristics of special fluids in “heat pipes.” The objective of this type energy recovery process is to move the wasted heat from the hot and dirty exhaust gas stream into some useful process.Waste Heat Recovery in the Aluminum Melting Furnace.There are considerations, of course:1) What might the value be of the recovered energy?2) Can the recovered energy be used within the process? Within the plant? Or by theneighbors?3) What is the capital cost?4) Is the recovery process complicated?5) Will it take additional staff?6) Will it cause additional downtime on the melting line?7) Will the operations staff need to be licensed?Ideally, the process will be simple and inexpensive, the recovered energy will be very valuable, and the whole effort will cause little distraction to the aluminum melting process itself. These would be ideal."

Jan 1, 2011

By Rachel De Lucas

Current methods of hydrogen storage are an impediment to the transition of our energy infrastructure from a hydrocarbon to a hydrogen base. The transportation, handling, and storage costs of hydrogen gas account for a majority of its selling price. Magnesium hydride slurry is a safe, environmentally friendly alternative for hydrogen storage. If this form of storage is to be adopted on a large scale, a cost-effective method for recycling the enormous amounts of magnesium hydroxide byproduct must be identified. The solid oxide membrane (SOM) process can be used to recycle the magnesium hydroxide byproduct into magnesium metal, which can be reformed into magnesium hydride and reused for fuel storage. Conventional magnesium extraction/recycling technologies require a great deal of energy and create byproducts that are harmful to the environment and human health. The SOM process poses none of these detrimental effects and requires less energy and feed preparation. The economic viability of a facility that utilizes the solid oxide membrane process for the direct reduction of magnesium must be examined in more detail if industry is to consider it. Cost analysis data related to the commercial viability of a scale-up will be compared to two standard industrial processes: current magnesium production techniques including electrolytic and metallo-thermic processes. We have shown in our cost comparison that the SOM process is cheaper than these traditional techniques and that it is also comparable to aluminum's Hall-Héroult process in cost but with none of the environmentally harmful byproducts.

Jan 1, 2006

By J. K. Brimacombe

"Nearly all the easy things have been investigated in injection metallurgy. Water models have been used exhaustively to study mixing, gas distribution and flow in submerged jets. Mathematical models have been developed with their restrictive boundary conditions to quantify submerged gas jet behavior. While being valuable tools to our understanding of injection metallurgy, there is an obliqueness to their application. What we need now are measurements and modelling on the actual systems, hot and unfriendly, where gas meets liquid at temperatures above l000°C. This is where the challenge lies.AN APPRECIATONThere are those who follow the trail and there are those few who blaze new trails in search of novel concepts and processes. With his restless, inventive mind, Howard Womer is a trail blazer without doubt. Decades ago, he was a pioneer in the pursuit of continuous steelmaking with the WORCRA Process and, today, he is developing new processes for the treatment of waste. He is not only an inventor but has been a professor at the University of Melbourne and was the first Director of Research at BHP. He has influenced the lives of many people, including myself; with his achievements and humanity. Therefore it is most fitting that this symposium should be held in honour of Howard Womer, a luminary in the metallurgical world for over half a century.BACKGROUNDGas injection has been an integral part of pyrometallurgical processes since the early days of Bessemer, then of Pierce and Smith. Today, of course, one cannot imagine pyrometallurgical processes without submerged gas injection to effect reactions for metal extraction and refining, to provide mixing and to inject solids into molten metal, slag or matte. Spurred on by new developments like tonnage oxygen and argon production, the Savard-Lee concentric tuyere and porous plugs, new steelmaking processes have emerged; and now solids injection is changing copper extraction processes. The ingenuity of the extractive metallurgists who drove these developments is inspiring for they have applied gas injection to transform pyrometallurgical processes. Humankind has been the beneficiary.' Today these processes are safer, more efficient, cost effective, less energy intensive and more environmentally friendly."

Jan 1, 1996

By Vinod K. Namilakonda

In situ synthesis of discontinuously reinforced aluminum alloy metal matrix composites was investigated. Aluminum alloy (A356: Al-7 wt% Si) was reinforced with dispersed AlN particles. Thermodynamic calculations were made for the composition determination of various phases formed during bubbling of NH3 gas into the Al alloy melts in the temperature range 1173-1473 K. Experiments were carried out for in situ production of AlN particles with the reaction between Al melt and NH3 gas in high temperature resistance furnace at 1473 K. The products were characterized using SEM, EDS and XRD. Effect of bubbling time of NH3 gas on the AlN formed in the composites was studied. The amount of AlN reinforcement in the Al alloy composites was observed to be in the range of 5 to 35 wt%. Good agreement was observed between the experimental and thermodynamic calculated data on the composition of AlN in Al alloy composites.

Jan 1, 2006

By A. V. Tarasov

Regeneration of carbide waste from hard-alloy (sintered carbide) manufacture is an important scientific and technical objective aimed at improving the degree of recycling of rare metals (W, Co, Ta, Ti, Nb). Currently, the degree of recycling of those metals does not exceed 25% to 35% of their total production even in industrially developed countries. This is attributed to a significant extent to the substantial drawbacks of the technologies applied for their processing (environmental pollution, limitations to the use of regenerated products for important applications, sophisticated equipment to be used). An innovative environmentally sound technology has been developed in the Institute of Metallurgy of the Russian Academy of Sciences (IMET RAN) for processing of carbide waste of WC, TiC, TTC and other carbides using asymmetric alternating current of industrial frequency (the electrolyte used for this purpose is nitric acid solution). The current efficiency under optimal conditions is as high as 96% to 98%. The process has been tested on bench scale. The following commercial-grade products are obtained: pure ammonium paratungstate, tungstic acid, cobalt oxide, titanium dioxide and tantalum-niobium concentrate. The total metals recovery is 98% to 99%.

Jan 1, 2006

By Thomas M. Harris

Cation exchange is not sufficiently selective to be used for the removal of heavy metal ions from a general industrial wastewater. However, if the metals can be converted to polyvalent anions through complexation, they may be removed both selectively and efficiently by anion exchange. This approach, referred to as chelation-assisted anion exchange (CAAE), has been examined using industrial wastewater samples contaminated with Ni2+ and Cr3+. For this particular application, the Ni2+ is complexed with 8-hydroxyquinoline-5-sulfonic acid, and the Cr3+ with sulfosalicylic acid. Removal efficiencies and adsorption isotherms for both the complexants and the complexes were determined in batch-mode tests.

Jan 1, 1994

By Yong Zhao, Yan-hui Sun

Behaviors and evolutions of MgO·Al2O3 in non-oriented silicon steel during calcium treatment were investigated by thermodynamic calculations and high-temperature experiments. MgO·Al2O3 inclusions were the main type of inclusions before calcium treatment, which is also confirmed by the stability diagram of MgO/MgO·Al2O3/Al2O3 from thermodynamic calculations. After calcium treatment, the majority of original MgO·Al2O3 inclusions were mainly modified to CaO-MgO-Al2O3 system inclusions, this would be beneficial to improve castability and product quality of silicon steel. But there was no modification happening to some MgO·Al2O3 spinels which were directly surrounded by CaS inclusions. The content of Al2O3 occasionally existed a sudden increase besides a common decrease in the product layer of CaO·MgO·Al2O3. Then the evolution mechanisms of MgO·Al2O3 inclusions were proposed in present work. Thus, Al/Mg atom ratio had a significant influence on the modification of MgO·Al2O3 spinel.

Jan 1, 2016

By Z. Smieszek, Z. Szota, P. Gajowski

"A new method for measuring the total quantity of suspensions contained in the electrolyte during copper electrorefining has been developed by the Institute of Non-Ferrous Metals, Gliwice. Electrolyte purity, and the suspensions content in particular, is of essential importance for the quality of electrolytic copper produced during the process. Suspensions contribute to the increase of slime impurities in electrolytic copper and increase losses in noble metals. Up to now, the laboratory method has been used for the· process control which provides analytical results with considerable time delay. Therefore, it is useless for the process control.The measuring method developed enables continuous measurements of a suspensions content directly within the stream of the flowing electrolyte. The principle of measurement is based on changes in optic properties of the electrolyte with varying suspensions content.1. IntroductionIn copper electrorefining, it is essential that the final product quality be maintained. If suspensions are present in electrolyte, the content of slime impurities in electrolytic copper, (such as Pb, Ag, Bi, Sn, Sb, and As), increases which can result in the occurrence of the so-called slime dendrites on cathodes, thus debasing the quality of the product. As a normal suspension content in electrolyte, the contents in the order of several mg/l are considered, usually not more than 5-6 mg/l, while contents exceeding 20 mg/l are referred to as an alarm state. Suspensions present in an electrolyte are usually a light fraction of anodic slime whose main components are metallic silver, lead sulphate, complexes of antimony and arsenic, and sometimes even calcium sulphate; they are mainly composed of very small particles of lead sulphate and antimony complexes. Sometimes - - in case of alarm states - - the so-called ""wandering slims"" can be observed, which are composed mainly of arsenic and antimony complexes. These ""wandering slims"" make a serious technological disturbance. In normal operating conditions of the electrorefining plant, an increase of suspension content can result from such reasons as crack of filter cloth in a slime filter, turbulent flow of the electrolyte, anodic passivation, aeration of the electrolyte, and improper servicing of an electrolytic tank. It is necessary to continuously control the suspensions content in electrolyte for proper electrorefining."

Jan 1, 1989

By Pekka Hanniala

The falling real price level of copper metal and changes in the treatment and refining charges has been characteristic to the copper industry during the last few decades. Outokumpu's continuous development of the Flash Smelting Technology and increased productivity of the smelters based on these improvements may be one of the basic reasons that have influenced to these trends. From the early beginning of the Flash Smelting Technology, it has been characterized by low operation costs and low emissions, and the vision has been to develop the technology towards Direct Blister Flash Smelting. In Direct Blister Flash Smelting, both smelting and converting are carried out in one furnace making it possible to reduce the number of unit operation steps and thus lower both operation and investment costs. The merger of large copper production companies taken place during the last few years is a sign of a new age in copper production business. Now, the aim is to increase the productivity of copper production not just by utilizing the economy of scale but also by increasing integration and optimization of the whole production chain from mine to refinery. This also means increasing win- win based cooperation between companies. A Production Network concept based on the Flash Converting process enables existing smelters to decrease the operating costs and expand the smelting capacity with minimum investment and at the same time to decrease the emissions of the smelters. The new structure in ownership and partnership between copper production companies makes it easier to adopt the Production Network concept to both new and existing plants, where there exists a lot of built-in capacity. The paper presents Outokumpu's prediction on how the new options for the smelters will contribute to further changes in the structure of copper production. These visions are illustrated by giving examples on how the combination of matte production, Flash Converting, and Direct-to-Blister Flash Smelting could be adapted in existing and new smelters.

Jan 1, 2002

By Guo Jun

In this study, BaTiO3 ultrafine particles surface-modified with stearic acid were synthesized by the hydrothermal method in a system of BaCl2-TiCl4-NaOH. The effects of NaOH/TiCl4 molar ratio, Ba/Ti ratio and time on structure and morphology of BaTiO3 ultrafine particles were investigated experimentally. The formation mechanism of different crystalline BaTiO3 particles was discussed, and it is considered that in a hydrothermal system, the main factors determining BaTiO3 crystalline are H+ replacement of Ba2+ causing H+ deficiency and anatase growth units involving in crystal growth, which clogs the axial channel for Ba2+ transference. By means of increasing the alkalinity of system and barium content, H+ deficiency and involvement of anatase growth units in crystal growth could be effectively controlled. The results show that when molar ratio of NaOH to TiCl4 is 9 and ratio of Ba to Ti 1.5, and time 8 hours, high purity tetragonal BaTiO3 ultrafine particles with a narrow grain-size distribution and nonpolar surface are obtained at 240oC. The particles have excellent flowability, which is ascribed that the surface polarity of barium titanium powder modified with stearic acid is changed and the interaction between the particles is weakened.

Jan 1, 2006

By T. S. Bannos

Section 1417 of the Safe Drinking Water Act Amendments enacted by the O.S. Congress prohibits the use of lead containing solders for potable water systems in new construction or when making repairs. The legislature defines "lead-free" solder as containing less than 0.2% lead. In the development of a new solder it was recognized in addition to the lead free requirement, the alloy should perform as well as the popular 50/50 tin lead solder, both in application and properties. Another objective was to have only nontoxic elements. This led to the development of a 4.0% copper, 0.5% silver and 95.5% tin solder. Review of the merits of other alloy systems and the development of the physical properties along with test data are presented for the lead free tin. rich alloy.

Jan 1, 1990