Search Documents

By R. A. Alock

The character, occurrence and genesis of the three types of nickel deposits, sulfide, laterite and deep-sea nodule are described, highlighting the differences in mineralogy and chemical composition that effect the extractive metallurgy of nickel and associated byproducts. World nickel production and current resources by deposit type and geographic location are also reviewed.

Jan 1, 1988

By S. S. Babu, T. Hong, T. DebRoy, S. A. David

"Oxide inclusions form in welds because of deoxidation reactions in the weld pool. These inclusions control the weld microstructure development. Thermodynamic and kinetic calculation of oxidation reaction can describe inclusion characteristics such as number density, size, and composition. Experimental work has shown that fluid-flow velocity gradients in the weld pool can accelerate inclusion growth by collision and coalescence. Moreover, fluid flow in welds can transport inclusions to different temperature regions that may lead to repeated dissolution and growth of inclusions. These phenomena are being studied with the help of computational coupled heat transfer, fluid-flow, thermodynamic, and kinetic models. The results show that the inclusion formation in steel welds can be described as a function of the welding processes, process parameters, and steel composition.IntroductionThe relationship between inclusions and formation of a high-toughness phase, namely acicular ferrite in low-alloy steel welds, is well known (1-4). Past research has focused on maximizing acicular ferrite amount in welds by controlling welding processes, process variables, and welding consumable parameters. Research has shown that there is a complex interaction between inclusion characteristics, prior austenite grain size, and weld metal hardenability. In a low-alloy steel weld, the small addition of titanium lead to a change in the inclusion composition and resulted in a transition in the microstructure from bainitic to acicular ferrite [see Fig. I]. This in turn lead to the best combination of strength and toughness. This paper describes the inclusion formation in low-alloy steel welds."

Jan 1, 1999

By E. Açma

In this study, the production of Cu, Co, and magnetic iron oxide from the ancient copper, slags, located in Küre-Turkey, is investigated. In the process under development, fayalitic slags containing 1% Cu, 0.43% Co are reduced in a D.C. arc furnace with coke or graphite additions. A metallic alloy, consisting of 3.8% Cu, 3.3% Co, 2.1% S, and the rest being Ice, is produced by granulation of the liquid metal. About 85% recoveries of Cu and C:o are achieved by hot sulfuric acid leaching of these granules followed by H2S precipitation. The, production of magnetic iron oxide is possible from the discarded leach solution, loaded v:ith FeS04, by using a method with geothite precipitation, dehydration, controlled reduction, and re-oxidation steps. The magnetic oxides produced have 20 m2Jg surface area, 1:8.3 aspect ratio, and the coercivity of 330-380 Oersted.

Jan 1, 1993

By ChuanJie Cai, Zemin Zhuang, Jing Chen, Xuebin Hao, Shaobo Zheng

"Carbon which was used as heating and reducing agent in traditional iron and steel making process at present brought us large amounts of greenhouse gas harmful gases and dust seriously leading to the fog and haze condition. As one of ideal global new energies, Hydrogen has good features such as rich resource, high heat efficiency, cleanness, renewable and transportation. With the commercialization of hydrogen energy, the world energy structure will be changed greatly. Although many scholars have done a lot of researches and long-term exploration on hydrogen metallurgy, researches on the formation of metal iron phase in the process of hydrogen reduction of iron oxides in slag was rarely reported, which had important theoretical significance on the development of hydrogen smelting reduction process. Based on the thermodynamics and kinetics calculation, A laboratory experiment has been designed to research the iron phase formation during hydrogen reduction of iron oxides in the molten slag in this paper. SEM and EDS techniques were also used to observe and analyze the iron morphology. According to detection results, the influence of temperature, reaction time and surface tension on the morphology of the iron phase reduced were showed.IntroductionWith the increasingly severe global warming greenhouse effect, governments are paying more attention to no-carbon and low-carbon energy development and utilization. Hydrogen has received widespread attention around the world, which has rich resources, high thermal efficiency, large energy density, use clean, transportation, storage, renewable etc [1].The development of the hydrogen economy is new competition areas of the world economy for the 21st century. China should assess the situation, and achieve the important strategy of peaceful development as the realization of new industrialization, by establishing a ""hydrogen economy"" industry revolution which replaces fossil energy. The current hydrogen metallurgy process includes hydrogen direct reduction, smelting reduction and direct steelmaking process. Hydrogen plasma hydrogen metallurgy is the use of hydrogen as a reducing agent to replace carbon reductant, to reduce carbon dioxide emissions, and to ensure the sustainable development of ironmaking industry."

Jan 1, 2014

By Pascal Gardin

The purpose of the paper is the mathematical modelling of flows inside steel continuous casting mould. For CFD validation of flow oscillation prediction, unsteady calculations with a realizable k- model were performed in a billet caster with rectangular section. Self sustained and regular oscillations were obtained. Calculated flapping frequency is very close to what is mentioned in literature. For slab caster configuration, flow oscillation is influenced both by lower roll, which creates very small frequency oscillation (0.012 Hz for our water model), and upper roll, which creates slightly higher frequency oscillation (0.05 Hz). The two rolls interact and it is possible to detect both frequencies in the nozzle jet region. Numerical results are in good agreement with measurements for fluctuating velocity spectra and provide explanation for interaction of rolls. To improve flow stability inside the mould, it is established that gas injection in the nozzle has a very positive effect.

Jan 1, 2006

By J. E. Wey

Extraction of cobalt from cobalt sulfide and cobaltite flotation concentrate from the Blackbird Mine, Idaho, was investigated using an adapted strain of Thiobacillus ferrooxidans. Cobalt extractions as high as 100% were realized in the inoculated experiments, whereas only 4% extraction was obtained in the sterile run. The influence of pulp density on the rate and extent of cobalt extraction was also determined. It was found that the extraction of cobalt followed predominantly the indirect mode of bacterial activity. In this process, ferric iron oxidizes cobaltite to cobalt sulfate and ferric arsenate while being reduced to its ferrous state; the bacteria continuously re-oxidize ferrous to ferric iron. Electrochemical measurements using cyclic voltammetry suggested that cobaltite oxidation involved a number of intermediate reactions.

Jan 1, 1993

By C. D. Seybert, J. W. Evans

"The elimination of convection is essential in experimental investigations of diffusive transport (of heat and matter) during solidification. This paper describes an investigation of an approach whereby a magnetic field gradient is applied to a electrically non-conducting diamagnetic liquid. A magnetic body force then arises which is dependent on the volume susceptibility of the liquid and thereby on the density. With the field gradient aligned vertically and of correct magnitude, the variation of gravitational body forces due to density variations (arising from temperature variations, for example) can be counterbalanced by a variation in magnetic body force.Preparatory to a study of convection control in diamagnetic liquids, PN measurements have been made of the convection occurring during the solidification of water. A peculiar flow arises because of the density maximum at 4°C. Modeling of the flow the steady-state solidification of water in an extremely high field magnet at the NHMFL indicates that flow can be significantly reduced, but it is suggested that, due to field gradient variations within the cell, flow cannot be completely halted. INTRODUCTIONNatural convection is inherently a part of terrestrial solidification. Density-based convection during solidification, due to gradients of temperature and/or concentration, has a significant effect on a material's properties. The design of products with specific material characteristics has required the development of many processes to control convection (such as in the growth of semiconductor crystals, and electromagnetic stirring in steel casting). The expansion of fundamental knowledge about the process of solidification requires collecting data in the absence of density-based convection, while most of science's solidification data (and thus the equations that science has fitted to those data) have been obtained under the influence of gravity. Only relatively recently, through clever experimental design (e.g., drop towers, high altitude parabolic flights, and space laboratories), have investigators been able to study solidification in an environment with ""micro-gravity""."

Jan 1, 2001

By Ma Shao Xian, Li Dong, Li Zhen Guo

"The new type shaft calciner ( SK-10 Serials) is developed and designed by CADRE itself on the basis of the conventional shaft calciner. The actual application in a number of calcinations plants have proven that they are of very good effect. Calcined coke calcining heated by the shaft calciner has a high quality, lower lost by fire. The shaft calciner needs no additional fuel when it is working. Anode Carbon Plant and calcined coke Plant commonly used the shaft calciner in domestic. The waste heat from the shaft calciner can be recuperated to generate electricity and to make the steam for produce. Exhaust waste heat is recovered by 90% or more. The new type shaft calciner's structure is optimized by computer simulation for fire-wall structure, combustion air to fuel ratio, volatile combustion is fully in use, furnace cooling zone structure, the exhaust smoking structure and calciner heat balance. Furnace structure and production operating parameters has been got the best optimized results. This paper introduces the working principle and characteristics of the shaft calciner - the equipment for calcining of the petroleum coke. It also demonstrates measured process parameters of the new type shaft calciner. Through comparison with the rotary kiln and conventional shaft calciner, it proves its own technical characteristics and advantages: higher capacity, high quality products, provides more energy for power generation, equipment operation and maintenance costs lower.IntroductionChina's petroleum coke market is mainly dominated by the delay raw petroleum coke. Rotary kiln and shaft calciner are the main process equipment for calcined petroleum coke. As the shaft calciner burning less, no external fuel, waste heat utilization is high, long service life, the utilization rate in China is more extensive than the rotary kiln."

Jan 1, 2012

By R. H. Hanewald

INMETCO, a subsidiary of Inco Limited, is the only facility in North America that provides High Temperature Metals Recovery for nickel-, chromium-, and iron-bearing wastes. Since 1978, this process has prevented more than 775,000 tons of materials from becoming part of the nation's waste stream. The paper describes Inco's experience in metals recovery, traces the development and explains the operation of the High Temperature Metals Recovery Process, and examines the procedures and criteria used to determine whether spent catalysts meet process feed specifications. An overview of the current requirements for transporting spent catalysts is provided. The paper concludes with brief case histories of catalysts users employing High Temperature Recovery to manage spent catalyst.

Jan 1, 1995

Laminated ceramics have received widely scientific and commercial attention because their properties, such as mechanical properties and electrical properties, can be tailored by adjusting the structure, thickness and composition of the different layers. For example, ferroelectric Bi4T13O12 (BIT) which has a positive temperature coefficient of dielectric constant (TE) can be used to modify the negative of typical microwave dielectric ceramic BaNd2Ti4O12(BMT). However, BaNd2Ti4O12/Bi4Ti3O12/BaNd1Ti4O12 (BNT/BIT/BNT) laminated ceramics could not be prepared by the general method because the optimal sintering temperature of BaNd2Ti4O12 ceramic (around 1350°C was much higher than that of Bi4Ti3O12 ceramic (around /1100°C). in this research, a new method of spark plasma sintering (SPS) combined with post-sintering was successfully proposed to prepare BNT/BIT/BNT laminated divided proposed to prepare ceramics. It was divided into three steps. In first step, the BaNd2Ti4O12 ceramics were prepared by conventional sintering method. In second mop, the calcined and pre-pressed Bi4Ti3O12 powders were sandwiched between BaNd2Ti1O12 ceramic pellets and spark plasma sintered at 900'C for 10min to synthesize BNT/BIT/BNT composite ceramics. In the last step, a post-sintering was employed to reoxidize the partially reduced BNT/BIT/BNT composite ceramics. The results of scanning electron microscopy (SEM) and electron probe mircoanalysis (EPMA) showed that BNT layer and BIT layer were well bonded and no significant interfacial infiltration between them was observed. The sandwiched BNT/B1T/BNT ceramic with 10.7% BIT in volume has a dielectric constant of 92.8, a low dielectric loss of 0.0068 and a small temperature coefficient of dielectric constant v/35 ppm/C at 1 MHz.

Jan 1, 2003

By Hal dun Kurama

In thus-study, Bigadic upper zone zeolitic tuff, which contains about 87% clinoptilolite was used as an ion exchanger for removal of Pb++, Cu++, Cd++ and Hg++ ions from wastewater. Bench scale experiments with two different glass columns, were carried out continuously under the closed/ open circuit conditions. Before ion exchange tests, zeolite samples were treated with NaCI (6ml/ min. and 42BV). The effects of particle size, bed volume, pH and flow rate on the ion exchange capacity were determined. Under the best operation conditions, the effect of initial influent solution concentration on ion exchange selectivity was tested. As a-result, it was found that the Bigadiç clinoptilolite had the following ion exchange capacities;

Jan 1, 1995

By Sadi Medina

As it is characteristic from Custom Smelters, ENAMl Las Ventanas Smelter has to deal with different qualities and quantities of mining products from about 70 suppliers, that contain a variety of impurities that would be harmful for copper production. In order to increase the smelting capacity, an oxygen plant has been running since September of 1990. Moreover, to improve the environmental conditions, a new sulphuric acid plant started up to neutralize the metallurgycal off-gases from the Teniente Converter and partially from the Peirce-Smith converters. Based on the on-line operation among the reverberatory furnace and the Teniente Converter using oxygen enriched air to produce high grade matte, most of the volatilizing impurities, mainly arsenic, are collected as discarding compounds in the gas cleaning system of the acid plant. This paper describes the continuous performance of the Teniente Converter with acid plant, the results attained, the operation problems and how they were solved. The impurities distribution achieved in this process is also included.

Jan 1, 1993

By Cong Wang, Kexin Jiao, Yongan Zhao, Haibin Zuo, Jianliang Zhang

The carbon composite brick is a new refractory used in blast furnace hearth and bottom. It caused wide attention due to its high thermal conductivity and low erosion by molten iron. In this paper, chemical constituents, SEM-EDS and X-ray diffraction were carried out in order to understand reaction mechanisms. A series of experiments of oxidation resistance characteristics were made. The oxidation mechanisms of carbon composite bricks in the presence of air were analyzed. According to the analysis on many experimental results, the oxidation process of carbon composite bricks under different temperatures were controlled by different mechanisms. In the condition of high temperature, SiO2 as oxidation product hindered the diffusion of O2, and reduced the oxidation loss of graphite in the internal.

Jan 1, 2015

By Peter Willbrandt

The flash smelter at NA was commissioned in March 1972 with an initial throughput of 50 tons of dry copper concentrate per hour. As a result of various measures, for example, oxygen enriched process wind, extension of the radiation part of the waste heat boiler, etc., the throughput could be increased to the present 70 tons per hour of dry concentrate. NA's plant is located on the outskirts of the city of Hamburg. The flash smelter's location and the growing awareness of the German population as regards environmental issues necessitate again and again considerable capital expenditure being spent on environmental protection. Thanks to the numerous small and large measures taken to protect the environment the emissions of dust, heavy metals such as arsenic, copper, lead, etc., and as well SO, could be drastically reduced. This paper will be giving an overview on the present state of the flash smelting process and the impact of the increasing environmental awareness at NA.

Jan 1, 1993

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 Stanko Nikolic

Ferrous calcium silicate slags are potentially important for future practice in copper converting operations and processes and can be described by the ?Cu2O?-FeO-Fe2O3-CaO-SiO2 system. Despite its industrial importance the phase equilibria in this system have not been fully investigated. Characterization of this slag system is necessary to improve the design and optimization parameters of new processes, including fluxing and operating temperatures. Experimental methods have been developed to investigate the phase equilibria of these slags at copper saturation and without copper. This technique involved equilibration of samples at a fixed oxygen partial pressure, rapid quenching, and analysis of the compositions of phases using electron probe x-ray microanalysis (EPMA). Liquidus and solidus data are reported for the primary phase fields of spinel, wollastonite and tridymite at 1250oC and an oxygen partial pressure of 10-6atm. The resulting data has been used to construct liquidus isotherms in the ?FeO?-CaO-SiO2 system both in equilibrium with and without molten copper. The experimental results were compared with the predictions of a thermodynamic computer package utilizing a self consistent thermodynamic database. The predictions of the model were in good agreement with the experimental isotherms when projected onto the FeO-CaO-SiO2 section, however the copper concentrations in the liquid phase at copper saturation were lower than predicted using the current database of the model.

Jan 1, 2006

By Mieke Campforts

The usefulness of the water-cooled probe technique to experimentally study slag solidification and freeze lining formation in pyrometallurgical reactors is evaluated. With this technique a layer of solidified slag is formed on a water-cooled probe that is submerged into a liquid slag bath. The influence of the submergence time and the heat input is examined. The solidified layers are analyzed with light microscopy, electron microscopy, electron probe micro-analysis and X-ray diffraction. Thermodynamic software is used to interpret the solidification microstructure. The results demonstrate that the technique is useful to understand freeze lining formation.

Jan 1, 2006

By Jefferson Caponero

The tire is an expressive component of Municipal Solid Waste, manly when its occupied volume is considered. Its treatment by pyrolysis stands for a list of advantages, such as: landfill releasing and a production of a high quality fuel. The exploitation of new natural resources is becoming more difficult each day, basically due to the environmental damages caused by this type of activity. This work presents a study on the thermal behaviour of Brazilian tires using thermogravimetric analysis and differential thermal analysis, in order to optimise the pyrolysis process of tires. Samples of I to 2 mm were investigated at atmospheres of nitrogen, argon, oxygen and mixtures of these gases at temperatures up to 1273K, under heating rates between 1 to 50 Klmin . The results showed that the behaviour of each sample is related to both the atmosphere composition and the heating rate.

Jan 1, 2001

By Timothy W. Skszek, Adrian S. Sabau, Hebi Yin, Gerard M. Ludtka, Xiaoping Niu

"A constitutive model has been developed to predict the yield strength aging curves for aluminum casting alloys during non-isothermal age-hardening processes. The model provides the specific relationship between the process variables and yield strength. Several aging heat treatment scenarios have been investigated using the proposed model, including two-step aging recipes. Two-step aging heat treatments involve a low temperature regime to promote nucleation of secondary phases and a second step at higher temperature for the growth of the secondary phases. The predicted results show that a yield strength of approximately 300MPa might be obtained in a shorter aging time, of approximately 30 minutes. As a result, better mechanical properties can be obtained by optimizing the time-temperature schedules for the precipitation hardening process of heat treatable aluminum alloys.IntroductionA356 is one of the commercially heat treatable aluminum casting alloys, and T6 is one of the heat-treated conditions to improve mechanical properties. The first stage of a T6 temper is solution treatment at an elevated temperature, generally in the range of 480 - 540°C. After solution treatment, the cast part is typically quenched in water/air to retain the solute-rich homogeneous matrix chemistry at room temperature. Subsequent ageing treatment stages capitalize on this super-saturated solid solution to generate controlled dispersions of very small strengthening precipitates within the matrix of Al grains [l]."

Jan 1, 2013

By Subagyo

The condition of slag in a pyrometallurgical reactor is vital to ensuring control of the process. A new technique based on multivariate image analysis (MIA) of digital images has been developed to provide an online measurement of important slag characteristics, such as the presence of exposed metal, the presence of solid phases, and temperature. This paper shall describe the technique and provide some results from analysis using industrial plant data.

Jan 1, 2003