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By Finlay Campbell

Nickel laterite pressure acid leach plants and reduction roast plants have had a checkered history in their engineering, construction, startup and operational reliability. Many potential projects have been the subject of detailed studies over the last thirty to forty years but relatively few have advanced to commercial production. Four reduction roast plants are currently operating, an additional one was partially constructed but never completed, and another was started up in 1974 and shut down after 12 years operation. Three acid leach plants have been built and commissioned in the last five years, trying to follow the example of the Moa Nickel plant in Cuba. An additional acid leach plant project is currently on hold, following limited construction work, its future subject to review by the owner because of potential cost over-runs. This paper attempts to discuss difficulties that may be encountered as a project is developed and will address factors which may affect production ramp-up schedule, long term production performance and overall production success. Comparisons are made with ramp-up performance at other large metallurgical plants that employ some comparable unit operations. Keywords: Caron, PAL, nickel laterite ore, ramp-up, reliability, process development, equipment design, step-out, commissioning, startup.

Jan 1, 2004

By V. M. Paretsky

The basic work conducted by Prof. A.Yazawa has demonstrated that in order to ensure single-stage white metal production by autogenous smelting of copper sulfide raw materials, it is most favorable to use highly basic slags, in particular oxide systems CaO-FeO-Fe2O3-Sio2. he special studies have been conducted in the Gintsvetmet Institute to investigate the composition and structure of slags produced on a semi-commercial scale when testing the KFP and FBP processes for white metal smelting, as well as the slag obtained in a full-scale KFP furnace at the Almalyk copper smelter. The investigations conducted have demonstrated why production of high-grade matte or white metal is associated with lower loss of copper in slag in a series: silicate slag I silicate-calcium slag I ferrite-calcium slag.

Jan 1, 2003

By Zhucheng Huang, Ronghai ZHONG, Tao Jiang, Jun ZOU

The method of reduction roasting and magnetic separation of low-grade, micro- fine disseminated refractory iron ore following granulation with coal produced unexpected success. Pellets of iron ore with diameter between 3 and 8mm were granulated with coal, bentonite and water. The raw pellets and reduction products were analyzed by scanning electron microscopy and x-ray diffraction. Results show uniformly distributed coal powders inside the pellets improved the kinetics of the reduction process and accelerated the reduction rate. Reduction time was higher at temperatures below 890℃, which resulted in the formation of substantial amounts of fayalite. When temperature was increased, micro- fine hematite was then quickly reduced to iron metal and the amount of fayalite decreased sharply. When pellets were reduced at 950℃ for 25min, reduction products with 56.73% metallization rate were obtained. After grinding and magnetic separation, a concentrate with 72.18% Fetot was obtained.

Jan 1, 2015

By Patrick R. Taylor

In the search for the development of more "environmentally friendly" and more intensive waste disposal approaches to meet more and more stringent environmental regulations, thermal plasma-based processes? are considered one of the most promising alternatives to well-established technologies such as incineration. This paper presents an overview on the research and development status of thermal plasma-based waste remediation technologies. The properties of thermal plasma are described. Due to its unique feature of high-energy intensity and super high temperature, thermal plasma is particularly capable of destroying organic-containing wastes. Its potential and promising application to waste remediation may include: treatment of incinerator ashes; metallurgical dusts (especially, electric arc furnace dust); medical wastes; radioactive wastes; and other Resource Conservation and Recovery Act (RCRA) listed hazardous wastes. Many research institutes and vendors have been involved in the development of thermal plasma-based waste treatment-technology encouraged by the cleanup programs supported by the Environmental Protection Agency (EPA), the Department of Energy (DoE) and the Department of Defense (000). More recently, thermal plasma-based waste treatment technologies (sometimes called plasma-enhanced pyrolysis) are focused more and more on not only just destroying organic wastes but also on how to practically, and economically recover energy contained in the organic waste materials in addition to the recovery of metals in order to offset the high operating costs.

Jan 1, 2003

"Many industrial processes involve materials that are subject to temperature change and thermal stress. Examples range from the casting of large metallic products to the cooling and reliability of small electronic components. Thermally induced stress is a major concern as it can lead to material damage and product failure. Material properties, thermal and mechanical, and process conditions such as the size and location of a feeder in metals casting, or the power dissipation in a computer chip, will govern the magnitude of these stresses. Temperature may also be influenced by fluid flow, for example, the airflow over a computer chip in a laptop will govern the rate of heat extraction, hence the temperature gradients in the chip and the evolving thermal stresses.This paper provides details on the governing equations for heat transfer (temperature) and solid mechanics (stress), their degree of coupling, and the numerical techniques used to solve them. Three examples are discussed to illustrate the use thermomechanical modelling. These also provide an insight into the degree of coupling required between the equations. The first example, involves thermal cycling of electronic components where a prescribed temperature field is applied. As temperature is known, this example only requires the solution of the stress equation. The second example also involves the modelling of an electronic component where the temperature field is also calculated. In both of these examples, the stress calculation is dependent on the temperature field, but the temperature calculation is not dependent of the solution of the stress equation (one-way coupling). The final example provides details on modelling the metals casting process. Both the temperature and stress equations are solved but, unlike the previous two examples, in this case the temperature field is dependent on the results from the stress calculation (two-way coupling)."

Jan 1, 2001

By Dietmar Eifler, Benjamin Jost, Marcus Klein

This paper focuses on the ductile cast iron EN-GJS-600 which is often used for components of combustion engines. Under service conditions, those components are mechanically loaded at different temperatures. Therefore, this investigation targets at the fatigue behavior of EN-GJS-600 at ambient and elevated temperatures. Light and scanning electron microscopic investigations were done to characterize the sphericity of the graphite as well as the ferrite, pearlite and graphite fraction. At elevated temperatures, the consideration of dynamic strain ageing effects is of major importance. In total strain increase, temperature increase and constant total strain amplitude tests, the plastic strain amplitude, the stress amplitude, the change in temperature and the change in electrical resistance were measured. The measured values depend on plastic deformation processes in the bulk of the specimens and at the interfaces between matrix and graphite. The fatigue behavior of EN-GJS-600 is dominated by cyclic hardening processes. The physically based fatigue life calculation “PHYBALSIT” (SIT = strain increase test) was developed for total strain controlled fatigue tests. Only one temperature increase test is necessary to determine the temperature interval of pronounced dynamic strain ageing effects

Jan 1, 2015

By Hassan Saalman, Mahmoud Mahmoud, Omneya El Hussaini

The Ferruginous sandstone ore was obtained from Ramlet Hemeyir area, Southwestern Sinai, Egypt, was found to contain 10% rare earth elements (REE). A representative sample has been subjected to sulfuric acid agitation leaching. About 93% of the REE content was released by mixing the ground sample to -100 mesh with concentrated H2SO4 at solid/liquid (S/L) ratio of 1/2 for 5h at a temperature ranged from 250 to 300o C. The REE was precipitated from the prepared sulfate leach liquor of pH 1.0 by adding 35% oxalic acid at 25o C. The precipitation yielded 98% REE. For selective separation of yttrium, the rare earth cake was leached with 31.5% nitric acid. Next, the aqueous solution was contacted with di-(2-ethylhexyl) phosphoric acid (D2EHPA) where 98% yttrium extraction was achieved. Stripping was done with hot H2O (80o C). Finally, a precipitation with oxalic acid was done followed by ignition at 950o C. A yield of 95% yttrium oxide was produced.

Jan 1, 2014

By A. A. EI-Geassy

High-grade iron ore fines rejected from the DRI plants (>96%Fe2O3) were isothermally reduced in 30-60%CO/H2 gas mixtures at 973-1273K. The freshly reduced reaction products were then subsequently carburised in either Hz/CO or H2/CO/S mixtures at 823-1 073K for 30-120 min. The thermogarvimetric technique was used to follow up both of reduction and carburisation reactions as a function of time. The carburised samples were characterized by X-ray and Mossbauer techniques. Chemical and carbon analyses were also applied. The influence of temperature and gas composition on the reduction behavior was investigated. The calculated values of apparent activation energy, application of gas-solid mathematical formulations were correlated with the microstructures to predict the reduetion mechanism. The influenee of carburization time, temperature, CO contents in H2/CO or H2/CO/S were investigated. A conversion extent of Fe to Fe3C was taken as a measurable index for the efficiency of carburization rcaction under the different experimental conditions.

Jan 1, 2003

By A. A. el-Geassy

High-grade iron ore fines rejected from the DRl plants (>96%Fe20) were isothermally reduced in 30-60%COIH2 gas mixtures at 973-1273K. The freshly reduced reaction products were then subsequently carburised in either H2/CO or H2/CO/S mixtures at 823-1073K for 30-120 min. The thermogarvimetric technique was used to follow up both of reduction and carburisation reactions as a function of time. The carburised samples were characterized by X-ray and Mossbauer techniques. Chemical and carbon analyses were also applied. The influence of temperature and gas composition on the reduction behavior was investigated. The calculated values of apparent activation energy, application of gas-solid mathematical formulations were correlated with the microstructures to predict the reduction mechanism, The influence of carburization time, temperature, CO contents in H2/CO or H2/CO/S were investigated. A conversion extent of Fe to Fe3C was taken as a measurable index for the efficiency of carburization reaction under the different experimental conditions.

Jan 1, 2003

By Krzyszof Borowiec

With the aim of determining the thermodynamic conditions for sulfation of impurity elements, in particular magnesium, in titaniferous slags the equilibrium gas composition for the sulfation reaction: MO + so2 + 1/2 02 = MS04 has been studied by an EMF technique with a solid zro2 + Cao electrolyte. Here M denotes the impurity elements: Mg, Ca and Mn, and the following _oxide systems have been studied: Ti02-MgO-Fe2 o 3 , Ti02-MnO-Mn2 o 3 , and Ti02 -CaO-Si02 , all in the . temperature range 700-1000ºc. Reproducible EMF values were obtained by adding small amounts of -Na2so4 to the oxide-sulfate mixture. From the observed results the Gibbs energy of formation of the phases Mg 2Ti04 , MgTi03 , MgTi 2o 5 , MnTi03 , CaTi03 , and CaTiSio5 , as well as the activity of MgTi05 in the solid solution with Fe2Ti05 have been calculated. The results show that, from a thermodynamic viewpoint, sulfation of these impurities in titaniferous stags i:s favorable- at around and below 800ºC.

Jan 1, 1985

By Petrus Christiaan Pistorius, Farzin Fatollahi-Fard

The production of synthetic rutile—a common starting material for most titanium production processes—from iron-rich titanium minerals such as pseudorutile and ilmenite is described. The process for “upgrading” the mineral to synthetic rutile is by carbothermal reduction of the mineral while immersed in a molten salt at high temperature, followed by magnetic separation of the reduced iron. A variety of factors are also investigated, such as particle size of the mineral, the type of mineral, and the molten salt used. The solubility of iron(III) oxide in different molten salts is also experimentally determined.

Jan 1, 2016

By Akita Ito, Sumio Kato, Mikio Sugai, Shinichi Nakata

"Spark Plasma Sintering (SPS) is a newly developed method for the sintering of metal and ceramic powders, and completes their densification at low temperature and in short period. The SiC powder was synthesized from diatomite and graphite or carbon black by heating at 1 450°C for 1 hr in an argon atmosphere. The synthesized SiC powder was heated at 1500-1800°C, 50 MPa for 15-18 min by SPS. The relative density of sintered SiC body increased with the rise in the temperature. The oxidation of the surface of the SiC particle and impurities in SiC from diatomite greatly influenced the sintering promotion of SPS.IntroductionThe SiC has high hardness because of the covalent bonding, and is also excellent in thermal and chemical stability. However, it is difficult to obtain a dense SiC sintered body by the combustion heating-method. Therefore, the dense SiC bodies have been made by the use of additives and I or the hot pressing (HP) method.In this study, the SiC powder was synthesized by using diatomite of natural products and graphite, and carbon black of reagent as raw materials, and the relationship between the properties of SiC powders prepared at various synthetic conditions and the density of sintered body by SPS was examined."

Jan 1, 2000

By E. Açma

Sivas-Divrigi flotation plant has a capacity of 90,000 tpy. Beneficiation of the tailings of iron ore magnetic separator seems to be attractive, because of its Cu, Co, and Ni contents. In the experimental work, sulfidic flotation concentrate is produced from these tailings. A roasting-leaching-H2S precipitation procedure is used to treat this concentrate, containing 0.55% Cu, 0.51% Co, 0.74% Ni, and 0.027% Zn. Sulfatizing roasting is carried out in a rotary furnace at 690°C. Roasted product is leached with 10 gpl HzSOl at 70°C and 30% pulp density. For the precipitation of desired metal, H2S is bubbled through the concentrated solution of repeated leaching, under controlled temperature and pH. Final metal recoveries of 91% Cu, 91% Co, and 50% Ni, and 92% Zn are attained. Roasting gases with their 13% SO2 content are suitable for H2SO4 production and the leach residues can be integrated with the iron ore processing plant as they contain 57.4% Fe and very low non-ferrous metals.

Jan 1, 1993

By J. L. Jambor

Previous crystal-structure determination of magnesian annabergite (Ni,MgMAsO4)2 8H2O indicated that ordering of Ni and Mg occurs in non-equivalent octahedral sites; such ordering supports the possibility of miscibility gaps on the Ni3(AsO4)2 8H2O -MgiAs04)2 8H2O. (annabergite-hornesite) join. In a predecessor study based on analyses of natural specimens, it was proposed that solid solution is incomplete both for annabergite-hornesite and annabergite-erythrite [Co, (AsO4)2 8H2O]. In the current study, syntheses by use of a slow-addition technique and aging of the precipitates indicated that the annabergite-erythrite solid solution is complete, and that no miscibility gap is present on the annabergite-hornesite join to at least 58 mol % Mg. Thus, interpretation of the compositions of these phases in oxidized mill-tailings impoundments can be done with the normal precautions for homogeneity, and without the added concern of the possible presence of miscibility gaps in the ternary system.

Jan 1, 1995

By Batric Pesic

Silver dissolution with thiourea was studied by using the rotating disk technique. The major parameters studied were: thiourea concentration (0-0.5M), ferric sulfate concentration (0-0.5M), sulfuric acid concentration (0-0.5M), and the effect of many foreign ions (Mn, o.i, Co, Ca, Na, etc.). Temperature effect was studied in the range 5-35 .C. The activation energy was 5.4 Kcal/mole. The dissolution of silver was first order with respect to ferric sulfate, and the secord order with respect to thiourea. Among the additives, copper had a dramatically negative effect. The strong oxidants such as hydrogen peroxide and manganese dioxide were also detrimental for silver dissolution. Silver does not dissolve with thiourea in the absence of ferric ions. Sulfuric acid does not participate in the dissolution reaction either. Chemically, the most important parameter for silver dissolution is the ferric sulfate/thiourea ratio. Thus, in the solutions with excess of ferric sulfate, a solid silver-thiourea complex is formed, which precludes transfer of silver into solution. In the solutions with the excess of thiourea, the free thiourea reacts with formed solid silver-thiourea complex and silver goes into the solution. The solid silver-thiourea complex was characterized according to its chemical composition. The complex contains 6.54%C, 2.49\H, 14.77%N, 16.09%0, 21.62%8, and 37.13% Ag. This composition corresponds to a Ag2so4.3'1U.2ff:i0 compound The soluble silver species are present in the solution as the dimers of AgTU+3 complexes.

Jan 1, 1989

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 Leah Penner, Thomas J. Ruth, Paul Schaffer, François Benard, Edouard Asselin, Stefan K. Zeisler, Thomas J. Morley

"This paper details the electrodeposition of metallic molybdenum from an aqueous, acetateelectrolyte containing molybdate ions. The deposition is carried out in a highly concentrated (up to I 0 M) acetate bath in the presence of a very low concentration of bone glue (60 µg/L). The molybdenum metal deposits are up to 20 µm thick and adherent. The deposits were characterized by XRD and XPS analysis. The deposition process is very inefficient, as up to 99% of the current is used to generate hydrogen during electrolysis. The effect of acetate concentration, pH, additives and current on the deposition efficiency and physical properties of the molybdenum deposit were investigated and optimized to obtain smooth, adherent coatings.IntroductionMolybdenum has increased thermal and wear resistance properties that are often utilized in material coatings [I]. These coatings are most often manufactured by sintering, pressing or spraying molybdenum powder at elevated temperatures, as a substitute method for standard metallurgical practices, such as electroplating [2, 3]. The lack of reports describing molybdenum deposition is most likely due to the highly oxophilic nature of molybdenum and the stability of its oxides, especially in water. Previous attempts to electrochemically reduce molybdenum from molybdate (Mool·) ions to molybdenum metal have reported the production of either a poorly adherent mixed oxide [4-6], or a thin(< 0.1 µm) metallic film [7-9]. Thick metallic molybdenum is capable of being co-deposited with one of the iron-group metals (Ni [10], Co [11] and Fe [12]) to produce an alloy [13, 14]. These alloys, however, may not be suitable for applications requiring pure molybdenum as they usually contain less than 50% molybdenum (often less than 30%)."

Jan 1, 2012

By L. Petitnicolas

The experimental study of nitrogen absorption and its removal from a liquid Ni-20%Cr alloy at 1873 K has been undertaken, using an experimental, apparatus based on the Sieverts technique in order to determine the solubility of nitrogen in the alloy. as well as the kinetics of nitrogen transfer across the gas/melt interface. Experiments show that nitrogen solute equilibrium content can be calculated using the Sievens law. Measurements point out the nitrogen absorption reaction rate to be well described by first order kinetics, whereas experiments on nitrogen removal reveal that the rate is better expressed using a second order equation.

Jan 1, 1996

By Jim Sundal

Primary steel manufacturers using electric arc furnaces generate one of the largest hazardous waste streams nationwide. The waste stream, known as electric arc furnace dust, is a listed hazardous waste with the designation K061. Oregon Steel Mills, Inc., (OSM) of Portland, Oregon, has implemented a process known as Glassificationn, which uses KO61 as an ingredient in an onsite recycling process. Because OSM was able to demonstrate that the Glassificationm recycling process beneficially uses all toxic constituents in the electric arc furnace dust and that the recycling process produces marketable products, the process is not subject to Resource Conservation and Recovery Act (RCRA) permit requirements. The marketable products manufactured using Glassificationn include roofing granules, ceramic glazes and colorants, abrasive blasting media and, more recently, synthetic slag fluidizers. The purpose of this paper is to identify the regulatory issues for recycling hazardous waste and demonstrate that OSM glass frit is effective as a slag fluidizer in primary steel manufacturing.

Jan 1, 1994

By Christian Hecker

An Eh-pH electrochemical sensor developed for on-line pH and redox potentials copper sulphide flotation process control was studied. The electrochemical sensor cell includes two metallic platinum electrodes, a metallic antimony electrode and a high impedance reference cell which are polarized with a potentiostat. For pH and redox potential determinations, the Sb and platinum electrode potentials are measured, respectively, against the polarized electrochemical reference system. The behaviour of this electrode configuration has been investigated in a laboratory scale. An electrochemical sensor device has been succesfully installed and checked in El Teninte Colon Concentrator&apos;s SAG line feeding the copper flotation rougher circuit.

Jan 1, 1999