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By Florian Aurelian, Mihai Popescu

"It will be tested four types of “geochemical barriers”. All those mixtures were contacted with mine waters containing uranium, radium and heavy metals. The loading capacity was determined. The optimum mixture was determined and its efficiency was tested within an uranium areal, where the activity was stopped. It was determined the possibility to recover the radioactive elements and the heavy metals from the investigated barriers.IntroductionThe paper presents the results concerning the performances of some “geochemical barriers” used for the decontamination of mine waters from uranium mining sites, which were tested in lab and in situ.ExperimentalThe research activity was carried out in lab and on the site.In the lab a module was constructed in order to follow up the uptake capacity of the “permeable reactive geochemical barriers” used to remove the radiolelements from the contaminated waters originated from the uranium mining industry. The barriers, which were used, are made of cheap natural materials, which can be easily got (wood chips, peat coal, sawdust, iron span, steel and zeolitic tuff). The following types of barriers were tested:•, 1st barrier: peat coal, sawdust, zeolite on weight ratio of 1/1/1;•, 2nd barrier: bentonite, sand, wood chips, peat coal on weight ratio of 1/1/1/1;•, 3rd barrier: iron span, steel, sawdust, peat coal on weight ratio of 2/1/1;•, 4th barrier: iron span, steel, sand, firry wood chips on weight ratio of 1/1/1.Lab researches concerning the uranium uptake capacity of the above described “reactive barriers” pointed out that the 3rd mixture (iron span, steel, sawdust, peat coal on a ratio of 2/1/1) didn’t reach the maximum uranium uptake capacity not even after eleven contact stages (the uptake capacity being of 70.6 mg U/ kg of mixture) and the mixture of peat coal, sawdust and zeolite has an uranium uptake capacity of 26.6 mg U/kg of mixture and becomes saturated after four contact stages.Each one of the components involved in physical-chemical processes of sorption, reduction and precipitation, will determine the diminution of uranium and other metals contents upstream the permeable reactive barrier."

Jan 1, 2008

By Rick Honaker

Rare earth elements (REEs) contained in coal and associated mineral matter exist in several forms including micro-dispersed minerals, ion adsorption onto clay surfaces, and chemically bound. Tests found that REEs can be effectively recovered from certain components of three coal sources by leaching under mild conditions followed by solvent extraction. A range of pH values were evaluated at solution temperatures of 25 and 75 °C. When using 1.2 M of sulfuric acid, nearly 85% recovery of the REEs was extracted from the middlings material collected from an operating plant. Acid leaching of a second middling source from another plant resulted in 60% of the total REEs being recovered under the same leaching conditions. Solvent extraction treatment of the leachate produced from six different coal sources resulted in products containing up to 50% total REEs from feedstocks starting with around 300 ppm.

"Mechanical alloying (MA) synthesizing technology and thennohydrogen processing (THP) were utilized to produce nanocrystalline Ti-MMC's reinforced by TiB intermetallic compound by using TiH2-B powder mixtures. Powders MA'ed up to 8 hours were examined by X-ray diffraction and SEM study. All MA'ed powders afterwards were HIP'ed at 700, 800 and 950EC for 1 hour. Detailed XRD, SEM and TEM study of the samples were carried out to determine the structure and micrography of the Ti-TiB MMC material processed by MA+THP approach followed by HIP'ing at high temperatures.IntroductionThe fiber reinforced titanium base composites [1,2] which possess a great resistance to high temperature have been investigated. In these studies fibers of C and SiC were used as reinforcing materials. However, these fibers react with Ti-matrix at elevated temperature resulting in product formation at the interface between the matrix and the fiber. Because of the chemical reactions, strength of the product MMC material diminishes.In conventional techniques of whisker reinforced composite material production, the mixtures of matrix metal powders and dispersed fibers are consolidated by hot pressing, HIP and/or hot extrusion. These techniques, however, have some shortcomings. Hard and brittle fibers could be broken during mixing cycle of the processing. Consolidation techniques could also be the cause for fiber breakdown. Attaining of the uniform dispersion of fibers into the metal matrix is not an easy process. The chemical reactions at elevated temperature exposures in the interface between the matrix material and fiber reinforcement cause product formations leading to poor mechanical properties."

Jan 1, 1998

By Torn H. Okabe

A fundamental study was conducted with the purpose of establishing an environmentally sound recovery process for recycling of valuable metals, by combining scraps containing such metals. As an example, direct extraction and recovery of neodymium (Nd) in magnet scraps was investigated by utilizing liquid metal as an extraction medium. It was found that liquid magnesium (Mg) is a suitable extraction medium and can extract Nd from iron alloys with high efficiency at around I 100 K. The newly developed extraction apparatus for Nd is a mechanically simple and static device without moving parts, where the Mg extraction medium circulates due to differences in the temperature inside the reaction vessel. This developed device can simultaneously accomplish continuous extraction of metal Nd from scraps, re-extraction of Mg from Mg-Nd alloy and the eventual recovery of pure Mg. As a result, metal Nd with 98 % purity was directly recovered from magnet scraps under certain conditions. It was also shown that the extraction agent Mg could be reused. The results of this investigation show the possibility of establishing a new process for the direct extraction of Nd in pure metal form without oxidization.

Jan 1, 2003

By Barry Welch, Kai Grjotheim

"The capital intensive nature of the present process for aluminium smelting, the low productivity per unit reactor, and pressure to reduce the electdcal energy demand have motivated the search for an alternative process. Optional routes include carbo-thennal reduction of alumina (using an alloy phase immediate), chlorination followed by electrolysis of aluminium chloride, and electrolytic decomposition of alumina using inert electrodes. Materials performance and reactor design constraints have been a major limitation for alternatives. However parallel research has led to considerable advances in the process efficiencies and scale of both the Bayer process and the Hall-Heroult cells.Future development of alternatives is dependent on breakthroughs in Materials Science such as the development of stable conducting anodes and stable wettable cathode materials. However if successful it is probable that some spin-offs will be retrofitted to existing cells. Therefore the basic Hall-Heroult technology will continue as the dominant process for at least the next half century.IntroductionThe present Bayer/Hall-Heroult process for production of aluminium is just over 100 years old. Frequently, during the century of its technological development questions have been raised as to whether it is the ideal route for metal production. The questioning was particularly intense in the period between the mid-1950s and the mid-1060s when the limitations of the Hall-Heroult electrolytic stage were evident. Then the cells were only 30 to 35 % efficient with respect to the utilisation of the hydro-electricity (requiring 16 18 kWh/kg, thus making it strongly dependent on cheap electrical energy), while the size of cells being installed were 80 to 130 kA. Hence the process was capital intensive, the productivity per reactor volume low, and the process was labour intensive (requiring about 15 man hours per tonne of aluminium). In addition, the use of pitches for Soderberg anodes and the fluoride electrolyte were creating problems through emission. At that time material science had paid little attention to the manufacture and use of carbonaceous materials or the development of alternatives that were corrosion resistant to cryolite or liquid aluminium. Hence cell lives were short - typically 600 to 1000 days - thus adding to operating costs. Thus the grass over the fence, as foreseen in 1960s vintage crystal balls appeared much greener for alternative processes."

Jan 1, 1988

By P. Koskinen

Outokumpu Oy has 30 years' experience in nickel production. It is mainly based on the technology developed within the company. The production chain starts from the mines reaching to the high-grade cathode nickel and the stainless steel manufacturing. As a multi-metal producer Outokumpu has the advantage to exploit from nickel raw materials also other valuable metals and intermediate products which can be processed at the company's various plants. The main source of nickel concentrate is nowadays the Enonkoski Mine started up in early 1986. It is the most modern mine in Finland being provided with the latest Finnish high-tech systems. Nickel concentrates are smelted at the Harjavalta Works using Outokumpu's internationally well-known flash smelting method. Also nickel containing residues and secondaries' are used as raw materials. The high-grade nickel matte from the smelter is then refined at the nickel refinery in a hydrometallurgical process, which was also developed by the company's own research staff. These processes have been continually improved and capacities gradually enlarged to 18 000 mtpy of cathode nickel. Besides plating, melting and superalloying purposes part of the nickel ends in stainless steel at the Tornio Works. The production was started in 1976 and has reached an established position on the European market.

Jan 1, 1988

By Zhi-xiang Cui

Effects of flux, vulcanizing agent and reductant on slag cleaning in new-type slag cleaning furnace (Φ3.6 × 8.1 m) were investigated under the conditions including smelting temperature of 1200 and 1250 °C, settling time of 30 and 60 min, and Fe/SiO2 of 1.7–1.9. The results show that addition of SiO2, B2O3 or CaF2 into original copper smelting slag can improve settling separation effect. Though no effect on copper recovery, addition of FeS can provide heat required by reaction with oxygen and reduce copper dissolution in spinel phase and slag. Copper content in discarded slag can be controlled at 0.26% under the optimum comprehensive conditions with ratio of oxygen to natural gas of 1.6.

By Torn H. Okabe

A fundamental study was conducted with the purpose of establishing an environmentally sound recovery process for recycling of valuable metals, by combining scraps containing such metals. As an example, direct extraction and recovery of neodymium (Nd) in magnet scraps was investigated by utilizing liquid metal as an extraction medium. It was found that liquid magnesium (Mg) is a suitable extraction medium and can extract Nd from iron alloys with high efficiency at around 1100 K. The newly developed extraction apparatus for Nd is a mechanically simple and static device without moving parts, where the Mg extraction medium circulates due to differences in the temperature inside the reaction vessel. This developed device can simultaneously accomplish continuous extraction of metal Nd from scraps, re-extraction of Mg from Mg-Nd alloy and the eventual recovery of pure Mg. As a result, metal Nd with 98 % purity was directly recovered from magnet scraps under certain conditions. It was also shown that the extraction agent Mg could be reused. The results of this investigation show the possibility of establishing a new process for the direct extraction of Nd in pure metal form without oxidization.

Jan 1, 2003

Although anion exchange resins are widely used for gold recovery in Russia and the former CIS, accounting for almost 50 percent of gold recovery in that part of the world, the technology has not been adopted in the West, apart from one small operation in South Africa. This situation is likely to change as the gold industry heads into the twenty first century. With gold prices having declined steadily through the 1990's, mining companies are under great pressure to reduce costs and improve gold recovery. Most studies on the use of resins for gold recovery from cyanide solution or pulp have shown that this technology has the ability to achieve both these goals. Resins can also be used to recover and recycle free and complexed cyanide in gold plant tailings, which has the potential to significantly lower operating costs, and latest developments in this area of technology are discussed. Finally, recent studies on thiosulphate leaching of gold have'shown that this process is very well suited to the treatment of carbonaceous, preg-robbing ores from the Carlin trend (Nevada, USA), and elsewhere in the world, because the gold thiosulphate complex does not load on to carbon. Whilst this obviously benefits the leaching process, it means CIP and CIL are ineffective in this situation, and the use of ion-exchange resins for gold recovery from thiosulphate leach solution are discussed.

Jan 1, 1998

By R. W. Bartlett

The extensive central Idaho black sand placer deposits are a potential source of rare earth elements, particularly the heavy rare earth elements that are not prevalent in commercial bastnasite deposits. These placers derive from the Idaho batholith. The geology, occurrence, and extent of these deposits are reviewed and the diverse mineral assemblages and complex mineral chemical compositions of these sands are described. Niobium, yttrium and thorium are also present in significant concentrations. The results of prior mining practice, including concentration and separation of the heavy minerals are reviewed. Technical approaches to extraction of rare earths from Idaho black sand concentrates are discussed.

Jan 1, 1992

By Hans von Michaelis

There has been a renaissance in gold and silver extraction and recovery that has taken place over the last fifteen years, since the price of gold was freed from the $3510~ level. Despite major advances in such areas as carbon adsorption processes for gold recovery, refractory gold ore treatment, crushing and grinding, process control, etc., there still remain several gold and silver mineral processing frontiers. Frontiers related to environmental management present significant challenges especially in the USA. More than ever it is appropriate to optimize total economics by adopting a "systems approach" that integrates mining, mineral processing and environmental management.

Jan 1, 1993

Kosaka Smelter & Refinery has a history of more than a century as a metallurgical department belonging to Kosaka mine. It has treated for a long time the "Black Ore" or the complicated concentrates dressed from it. The "Black Ore" is composed of black sulfides. It contains not only valuable metals such as gold, silver, copper, lead and zinc but also some impurities like arsenic, antimony and bismuth. With the development of Kosaka's floatation technology, five kinds of concentrates (copper, zinc, lead, pyrite and barite) have been separated from the "Black Ore" but the separation was not complete and each concentrate contained some unfavorable impuritie. In 1980s the highly appreciated yen and the drop of the metals priees forced many domestic mines to close their operations. Since then Kosaka Smelter has changed its way of operation to a custom smelter. Now more than 95% of copper concentrates are imported to take advantage of this technology of "Black Ore" treatment. It mainly treats the raw materials that contain high gold and silver like the "Black Ore". Recently, Kosaka has been working on the recycling of the metals from the printed circuit board scraps and sludge which contain some precious metals. The volume of the recycled metal is continuously increasing.

Jan 1, 2003

By Vladimir Panjkovic, Ostrovski. Oieg, Campbell Cripps Clark, John Truelove

"Effects of properties of raw materials and blast on the performance of an iron bath reactor have been examined by a mathematical model. The model consists of three modules: 1) chemical reactions in the gas phase and heat transfer from gas to droplets ejected from the bath; 2) heat losses from the vessel and radiative heat transfer from the freeboard to the bath; and 3) heat and mass balances for the bath. The following parameters of the process are calculated: coal, ore, flux and oxygen consumption, post-combustion ratio and heat-transfer efficiency, temperature and composition of the off-gas, and slag and metal chemistry.IntroductionOne of the anticipated advantages of smelting reduction over conventional ironmaking is the use of lower-grade raw materials. In this work, the effect of-properties of raw materials on the performance of an iron-bath reactor is examined with a numerical model. The model is also used to assess the effect of properties of the blast (flowrate, temperature and oxygen enrichment) and ejected droplets (generation rate, size and ratio of total weights of slag and iron droplets) on the key parameters of the process. In the process coal, oxygen, ore (which may be partly prereduced) and fluxes for specified slag composition are charged to the bath. Slag and iron droplets are ejected from the bath into the gas phase, where they are heated before returning to the bath. Iron droplets undergo decarburisation and reoxidation with CO2 and H2O. Dust is also generated from the bath, and oxygen or preheated air for post combustion is injected from the top of the vessel.The model consists of three modules: 1) reactions in the gas phase and heat transfer from gas to droplets ejected from the bath; 2) heat losses from the vessel and radiative heat transfer from the freeboard to the bath; and 3) heat and mass balances for the bath. The structure of the model and the data exchange between the modules are shown in Fig. 1. The following parameters of the process are calculated: coal, ore, flux and oxygen consumption, postcombustion ratio (PCR), heat transfer efficiency (HTE), off-gas temperature and composition, slag and metal chemistry, and rates of decarburisation and reoxidation of the iron droplets."

Jan 1, 1996

A novel pressure leaching process for platinum group metal (PGM) feedstocks is described. The process is particularly well suited for treatment of ores or concentrates that are too low grade for economic processing by the conventional smelting/leaching process. Operating conditions have been identified under which gold, the PGM's and the base metals dissolve simultaneously in a pressure leaching autoclave. The product of this leaching process can then be treated by one of several flowsheets, of which the preferred will likely involve solid/liquid separation, followed by precipitation (or adsorption on activated carbon) of gold and the PGM's, followed by copper solvent extraction/electrowinning. Depending on the concentrations of nickel and cobalt, the copper raffinate would either be partially recycled to the autoclave to allow NilCo concentrations to build up, or it would proceed directly to a Ni/Co refinery. This paper deals with the pressure leaching process and the recovery of gold and the PGM's from the pressure leach product.

Jan 1, 2000

By K. Walanabe

Kosaka Smelter & Refinery has a history of more than a century as a metallurgical department belonging to Kosaka mine. It has treated for a long time the "Black Ore" or the complicated concentrates dressed from it. The "Black Ore" is composed of black sulfides. It contains not only valuable metals such as gold, silver, copper, lead and zinc but also some impurities like arsenic, antimony and bismuth. With the development of Kosaka's floatation technology, five kinds of concentrates (copper, zinc, lead, pyrite and barite) have been separated from the "Black Ore" but the separation was not complete and each concentrate contained some unfavorable impurities. In 1980s the highly appreciated yen and the drop of the metals prices forced many domestic mines to close their operations. Since then Kosaka Smelter has changed its way of operation to a custom smelter. Now more than 95% of copper concentrates are imported to take advantage of this technology of "Black Ore" treatment. It mainly treats the raw materials that contain high gold and silver like the "Black Ore". Recently, Kosaka has been working on the recycling of the metals from the printed circuit board scraps and sludge which contain some precious metals. The volume of the recycled metal is continuously increasing.

Jan 1, 2003

By O. Durand

The Cerro Verde Hydrometallurgical Plant, located at Arequipa in the southern part of Peru, started its operation in 1977 with a design capacity of 33,000 MT/year of copper cathodes. The plant has treated 61,055,000 MT of ore mainly oxides with a content of 1.01% total copper and 0.67% of soluble copper. The leaching plant has three pads that produce 4.0 gpl copper solution. The solvent extraction plant has four trains with three extraction stages, two stripping stages with a single mixer in all stages. The mixer-settlers are 316 stainless steel and the pumps are vertical turbines. The flowrates of 1,300 gal/mil of aqueous and 1,300 gal/min of organic at a 1/1 ratio. The electrowinning plant contains 208 commercial cells and 18 starting sheet cells. Each cell has 47 anodes and 46 cathodes. In addition to describing the hydrometallurgical plant, this paper also mentions efforts directed at reducing costs and improving operations. The initial results from leaching secondary sulfides, which started October 1985, are also discussed.

Jan 1, 1987

By Mototsugu Matsuno

A new process has been developed to treat fly ash generated from municipal incinerators, which contains not only toxic metals such as lead and cadmium, but also dioxins. The process includes the following steps; fly ash is formed into green pellets with some additives and the pellets are then roasted to eliminate or stabilize the toxic metals and to decompose dioxins. A pilot plant with a capacity of approximately 100 kg/hr was used to test the process. The tests verified that heavy metals were either volatilized or stabilized and dioxins were decomposed by high-temperature roasting. The pelletized ash was found to be non-toxic, so that it can be recycled as artificial lightweight aggregate. It was also found that volatilized metals collected as secondary ash can be recycled as smelting resources.

Jan 1, 2003

By A. E. M. Warner

In co Limited has long and extensive experience in converting nickel-copper primary smelting mattes over a broad range of nickel/copper weight ratios and combined nickel-copper-cobalt contents. At the Copper Cliff Smelter, the composition of the converter product matte has to meet the requirements of the matte separation process; at the Thompson Smelter, converter matte of a different composition is cast into anodes for nickel electrorefining; and in Soroako, Indonesia, a very low copper product matte is granulated for the Japanese market. Recently, Inco has conducted pilot plant testing of three possible nickel-copper matte continuous converting routes, namely flash converting, oxygen top blowing-nitrogen bottom stirring, and tuyere blowing. This test work has generated substantial new information on nickel-copper matte converting chemistry. This overview paper reviews the metallurgy of nickel-copper matte converting, in particular the behaviour of cobalt and the operating conditions required to meet the iron and sulfur specifications of the product matte. The relevant thermodynamic information is used to discuss the industrial data.

Jan 1, 2003

"The theoretical basis of ideal smelting reduction using coal as reductant in a process employing closed loop forced-circulation of hot metal is outlined. In the proposed process, an extensive area of relatively slag-free hot metal is available as a heat sink for absorbing the large amount of heat produced by complete combustion of CO within the furnace. Any slag that is formed within the oxidizing arm of the furnace loop is quickly swept away as a thin floating layer by the bulk movement of hot metal which is induced positively by forced melt circulation and sustained by causing the hot metal and the thin slag layer to overflow into a lower level hearth in which coal is carbonised and dissolved directly into the circulating melt.The proposed process is shown to offer very substantial cost savings over all other direct smelting technology. This is mainly because of its inherently low capital cost and its high energy efficiency. Furthermore, the favourable economics are not reliant on fuel gas credits as all the process gas is combusted within the reactor itself.IntroductionMetallurgical processes in the year 2000 will be compromise solutions to the metallurgical problems that already exist today. It is common knowledge that the mineralogical complexity of certain polymetallic sulphides, for example, precludes high degrees of separation and recovery by conventional mineral beneficiation. steps are therefore being taken towards the development of a truly polymetallic smelting process which will produce simultaneously zinc lead and copper as, metals from complex ores without prior beneficiation(l). In the ferrous extraction industry, the shortcomings of the highly efficient modern blast' furnace are well known and world-wide there is considerable effort being directed towards coal-based ironmaking without the requirement of metallurgical coke as a process intermediate. The current status 0f2Joal-based ironmaking has recently been reviewed by Smith and Corbett. (2)"

Jan 1, 1988

By Rodney L. Williamson

Optimal estimation theory has been applied to the problem of estimating process variables during vacuum arc remelting (V AR), a process widely used in the specialty metals industry to cast large ingots of segregation sensitive and/or reactive metal alloys. Four state variables were used to develop a simple state-space model of the V AR process: electrode gap (G), electrode mass (M), electrode position (X) and electrode melting rate (R). The optimal estimator consists of a Kalman filter that incorporates the model and uses electrode feed rate and measurement based estimates of G, M and X to produce optimal estimates of all four state variables. Simulations show that the filter provides estimates that have error variances between one and three orders-of-magnitude less than estimates based solely on measurements. Examples are presented that verify this for electrode gap, an extremely important control parameter for the process.

Jan 1, 2001