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By Pragna N. H. Bhakta

The minerals industry is under political and economic pressure to reduce its processing wastes and minimize their impact on the environment: Recycling is one of the means by which the minerals Industry can reduce the quantities of effluents and residues that are discharged to the environment. The wise use of available resources is not only an environmental necessity but also an economic benefit as natural mineral resources are depleted and/or become more complex. The purpose of this paper is to review the technical and regulatory issues that will help shape the future of minerals recycling over the next ten years. Research and development to address technical issues will be discussed with emphasis on the Bureau of Mines recycling research program.

Jan 1, 1992

By John A. Mavrogenes

Reflected light microscopy and electron microprobe techniques were used to determine the mineralogy, phase percentages, grain sizes, and textures of Co-Ni-rich mattes. The mattes were produced by submerged bath smelting at the University of Missouri-Rolla Pyrometallurgical Center of a flotation concentrate with 4.S% Co and 5.1% Ni that was prepared at the United States Bureau of Mines Rolla Research Center by flotation up-grading of the cobalt and nickel content of a copper concentrate from the Magmont mine, Viburnum Trend, Southeast Missouri. Nine distinct phases were distinguished in the matte samples, and three of these contain cobalt and nickel. The phases that were free from cobalt and nickel are bornite, chalcocite, pyrrhotite, magnetite, metallic copper, and galena. Submerged bath smelting serves to segregate the cobalt and nickel into phases that can subsequently be recovered by flotation. These phases are: shandite (Ni3PbZSZ)' cobaltpentlandite ((Co,Ni,Fe)9SS)' and Co-bearing Fe-rich sphalerite ((Zn,Fe,Co)S). Most of the cobalt occurs in cobaltpentlandite, but some is present in sphalerite. High total air conditions during smelting favor the development and segregation of cobalt into cobaltpentlandite. Nickel occurs in cobaltpentlandite and shandite. Shandite contains lead, a deleterious constituent in the smelting of cobalt and nickel.

Jan 1, 1989

By V. M. Sokolov, Jr. DuPlessis

The technology for recycling fine wastes, grinding sludges or swarf, and solids such as slag that contain a high content of metallic material needed improving. The objective was to produce a master alloy that met the tight requirements of the Western manufacturers and achieve improved yields of the valuable elements, nickel and cobalt, to over 90%. The alloys from the production of Alnico. magnets were chosen for this work. A process is proposed .that is able to recycle all kinds of Alnico wastes. This process is able to reduce all detrimental elements, which are contained in the wastes, to within acceptable levels. Molybdenum, if present, is an exception. Depending on the levels of contamination of undesirable elements different recycling strategies are proposed. The majority of the wastes can be recycled by melting and refining with a liquid slag layer using unique melting furnaces that are relatively unknown in Western nations. The proposed technologies allow the reelamation of over 95% of the cobalt and nickel from any kind of Alnico waste, and there are no limitations on the proportion of different kinds of wastes in the charge. The proposed processes and technologies could also be applied to the recycling of grindings, turnin

Jan 1, 2000

By R. M. G. S. Berezowsky

Treatment of Hudson Bay Mining and Smelting Co. Ltd. (HBM&S) zinc concentrate in the Sherritt zinc pressure leach process produces a residue containing elemental sulphur, residual sulphides, precipitated iron species, si1ver and gold. Flotation of the residue recovers most of the elemental sulphur and residual sulphides to the concentrate, leaving iron oxides and bask sulphates in the tailings. The tailings also contain most of the sflver and some gold. Direct cyantde leaching of the oxide tailings (220 g/t Ag, 1.4 g/t Au) was capable of leaching most of the gold, but only a minor portion of the silver. This paper reports testwork, conducted by Sherritt on behalf of HBM&S, to define a process for a high recovery of the precious metals from the oxide tailings. A si1ver enhancement treatment, consisting basically of digestion of the residue with lime at 90°C to render the silver amenable to enhanced recovery by subsequent cyanidation, was selected as the most promising approach. Batch silver enhancement and cyanidation tests showed that treatment of the oxide residue with 80 kg/t CaO at 90°C for 1 to 2 h increased the silver extractability in subsequent cyanidation from <20% to 96%. A 96 h continuous miniplant test (1 kg/h solids feed rate), of a circuit including a silver enhancement treatment step followed by conventional cyanidation and carbon in pulp silver and gold recovery, confirmed metal recoveries to the carbon of 90% Au and 96% Ag. Reagent consumption rates were 1ess than 100 ?kg/t CaO and 5 kg/t NaCN.

Jan 1, 1990

By René Winand

Due to chemical and electrochemical behavior of the most common additives in copper electrorefining i.e. gelatine, thiourea and chloride ions, it is essential to simulate as far as possible true industrial practice while performing laboratory experiments. The three additives must be studied simultaneously, and added continuously to the electrorefining cell. Ratio electrolyte volume to cathode area; ratio bleed flow to cathode area; hydrodynamic conditions; residence time of electrolyte in the cell; current density; electrolyte and soluble anode must be as near as possible to industrial ones. Experiments performed in the author&apos;s laboratory show that under these conditions, reproducible results can be obtained at normal industrial current density and at high current density as well. Problems are however still encountered when developing a sensor for additives monitoring, due to electrolyte redox potential and to substrate influenced thin layer deposition.

Jan 1, 1995

By David Tisdale, Phillip Mackey, Nagendra Tripathi, Matthew Kreuh, Pascal Coursol

Xstrata Nickel’s Sudbury smelter operation is based on fluid bed roasting of Ni-Cu sulphide concentrate, followed by electric furnace reductive smelting and Peirce-Smith converting to produce a Bessemer matte for electro refining, along with sulphuric acid produced from smelter gas. While the site dates back to the 1930s, the present smelter configuration has been operational since 1978, and currently has a nominal capacity of about 67,000 tpy of contained nickel and is investigating options to expand in future up to 85,000 tpy. As part of a review of plant capacity options, a new metallurgical model of the plant was developed in order to examine a number of processing alternatives. Based on the METSIM™ platform, the present model includes the ability to examine the impact of a number of plant parameters on potential plant performance including; for example, the following: percent of sulphur elimination in roasting, matte grade, degree of matte metallization, temperature, coke requirements, sulphuric acid production, CO2 emissions and overall energy requirements. The process model also includes a number of special features adopted; for example, approaches to effectively model the complex Ni-Cu-Co-Fe-S-O matte system. This paper provides a description of the model and gives an overview of the results. As well as presenting the results of the present study, the applicability of this modeling approach to pyrometallurgical systems in general is also briefly discussed in the paper.

Jan 1, 2009

By Henk Dijkman

Existing metallurgical operations can be optimized by implementing engineered bioreactor systems in the process configuration. For instance, metals can be recovered safely and economically from process and waste streams using biogenic sulfide. This paper focuses upon possible applications of high rate biotechnology in metallurgy and mining. Metal recovery from liquid streams (process bleed streams, leach water, waste streams), integrated removal of (fugitive) SO2, treatment of acid blowdown and other options will be described. Practical examples are given. A large-scale application of biotechnology at Pasminco&apos;s Budel Zink refinery is described. Here, acid plant blowdown is treated together with electrolyte magnesium bleed. Concentrated zinc sulfide (10 tpd) is produced biologically, eliminating the production of gypsum and closing the refinery sulfur cycle. Recovery of metals from solution at Kovehute Pribram in the Czech Republic is the second practical example. In this case, H2S is produced on-site for metal removal from an alkaline slag dump leachate. At the Caribou mine in New Brunswick, Canada, acid mine drainage is treated with biogenic sulfide. This plant is situated upstream of a lime neutralization plant. As a result, reusable ZnS is produced, the volume of the sludge (gypsum and hydroxides) from the lime plant is reduced by 50%, the sludge is free of heavy metals and the final effluent concentration of heavy metals is in the ppb range. In the second phase of this project, metals will be recovered from stored tailings, resulting in significant revenues.

Jan 1, 2002

By C. Geenen

At its Olen site, Union Minière Copper operates a new full-size deposit tank house. A first 200,000 t/y module was commissioned in October 1996, and an additional 130,000 t/y unit started in April 1998. The main objectives of the new tank house project were to produce grade A cathodes starting from anodes with a wide range of compositions and at a minimal operating cost. The tank house uses Isa Process technology. Based on the process parameters agreed upon with MIM, UM Copper developed the basic design and UM Engineering was the in-house contractor for the engineering. The new tank house is equipped with advanced technology polymer concrete cells, automated two-bale cranes and high-capacity machines. The first 200,000 t/y module treats anodes with a more conventional composition at 330 A/m2; the second 130,000 t/y module treats anodes with a high slimes fall (12- 13 kg/t) at current densities up to 285 A/m2. After some teething problems, the new tank house is meeting all set targets. This paper illustrates and comments on the design characteristics and operational results.

Jan 1, 1999

By H. Kamiya, H. Hasegawa, M. Nojiri, S. Matsui, Y. Fukuda, M. Tsukada

"The present paper focuses on the action mechanism of anionic polymer dispersants in dense Si3N4 and SiC suspension. An atomic force microscope (AFM) was used to determine the relationship between the macroscopic suspension viscosity and the microscopic adsorbed structure of a polymer dispersant at the solid / liquid interface. The surface interactions within the suspensions were analyzed in various dispersant pH and additive conditions. The addition of an anionic polymer dispersant decreased Si3N4 and SiC suspension viscosity and increased electro-steric repulsion force on the non-oxide surface in solution at pH> 6 which was the isoelectric point of the materials. It was assumed that the increase of repulsive force was promoted by a hydrophobic adsorption of polymer dispersant on the non-oxide particles.IntroductionThe surface of silicon nitride and silicon carbide powders in a water suspension system has quite a complex molecular structure. In the case of Si3N4, hydroxyl and ammonium groups form on the surface and the pH of the suspension is increased from neutral to about 10 due to surface oxidation. The particle surface is negatively charged in alkaline solutions (pH=10), because the isoelectric point of silicon nitride exists in the pH range from 5 to 6. However, in spite of charging the negative surface charge, an anionic polymeric dispersant is generally used for the reduction in slurry viscosity.In dense SiC suspensions, an anionic polymer dispersant is generally used in order to disperse aggregates and reduce the suspension viscosity, too. Since an anionic dispersant is used in alkaline solutions higher than the isoelectric point of silicon carbide, the dispersant adsorbed on the negative charged surfaces of SiC.Few researchers have discussed and estimated the adsorption mechanism and structure of anionic polymeric dispersants on silicon nitride and silicon carbide surfaces. This is because it is difficult to observe the structure and measure the interaction at the solid/liquid interfuce directly. However, new developments in surface-force measurement technology have enabled the determination of non-DLVO type interaction for analyzing aggregation behavior2. The use of the AFM for analyzing the effects of various surfactants and co-polymers on colloidal dispersions and solid surfaces has also begun to rapidly expand to characterize the interaction between solid surfaces."

Jan 1, 2000

By Frank Field, Elsa Olivetti, Randolph Kirchain, Elisa Alonso, Gabrielle Gaustad

"The primary technological challenge to increased use of secondary raw materials is the presence of undesirable elemental species in scrap streams. Recent literature indicates that this may become exacerbated by accumulation of impurities over time. Devising strategies to mitigate this problem depends upon understanding the mechanisms of accumulation. This paper takes a first step at characterizing the extent of this issue by presenting a simple analytical model of recycling rate for materials experiencing exponential growth. Low potential recycling rates limit accumulation due to dilution. Empirical analysis of several major materials indicates that, even for current recovery rates, theoretical recycling rates can reach above 60%, making accumulation issues a possibility.IntroductionIt is well known that recycling of secondary materials can provide significant environmental and economic benefits. Energy savings, in particular, can be quite large when substituting secondary materials for primary. Nevertheless, over the past decade, the recycling rates within the U.S. of many materials appear to not be increasing as rapidly as one would predict or even at all (Figure 1). While many barriers exist to increasing materials recycling, one that is cited consistently by the literature and producers[1-3] is compositional limitations; that is the mismatch between the characteristics of secondary materials and those desired for the finished goods into which they would be transformed..One particular aspect of compositional limitations that is receiving increasing attention is the potential for progressive deterioration of the quality of secondary raw materials streams. For some materials, for example paper or polymers, this phenomenon is inherent and relatively rapid[4, 5]. As such, it is well documented and plays a significant role in recycling decision-making even for prompt or in-house material recycling. Conceptually, this issue can manifest in other secondary materials as well, albeit through a different mechanism.As materials are mixed, used, and reprocessed during recycling, they come into contact with and often pick up other elements. The presence of these, so-called, tramp elements alters the original known composition, possibly requiring additional measurement and processing and may even preclude economic, productive reuse; ultimately, this unintentional pick up is unwanted. A growing number of studies and literature would suggest that accumulation of unwanted elements is an emerging problem, in most recycled material streams. Table I provides a brief literature review of various recycled material streams and the accumulated elements noted as problematic by various authors"

Jan 1, 2008

By L. Klinger, T. Werber, LA Levin, A Katsman

"The process of catastrophic carburization known as ""metal dusting"", whereby a solid metallic material is converted into fine particles in a carburizing atmosphere, was analyzed. It was shown that this conversion is the result of plastic deformation and subsequent fracture accompanying diffusional phase formation in the near-surface layer. The process is controlled by internal stresses arising during phase transformation. Competition between stress generation and relaxation may result in the attaining the ultimate strength in the near-surface layer and its fracture. Such a mechanism of metal disintegration may occur in a certain temperature interval depending on the kinetic and geometrical parameters of the system - the diffusivities of the alloy's components, the ratio between specific volumes of the new and the old phases, and the ultimate plastic strain. The temperature interval for disintegration of carbon steel, the rate of disintegration, and the period of the disintegration cycle, were evaluated and compared with experimental data. IntroductionCatastrophic carburization, known as ""metal dusting"", consists in conversion of a solid metallic material into fine particles. The process occurs in a carburizing atmosphere at elevated temperatures. The corrosion product, usually named ""coke"", consists of metallic particles dispersed in a loose carbon matrix. Under industrial conditions metal dusting takes place, for example, in a gas mixture of CO and H2 or in hydrocarbon environments. Steels, nickel- and cobalt alloys are susceptible to this kind of wastage in the temperature range 400-800°.A mechanism of metal dusting in steels was proposed by Hochman [1] and later developed by Grabke and coworkers [2-5]. According to the proposed model, the process consists of the following reaction steps:"

Jan 1, 1996

By John T. Berry, Robert D. Pehlke, Michael J. Beffel

"Pattern making and metal casting organizations are currently adopting CAD/CAM systems and implementing this technology in design and production. Al though significant progress has been reported, these systems generally are based on two or two and one half dimensional analyses. Very few are based on solid geometric modelers.The present paper emphasizes the need for solid geometric modeling of the casting and rigging system and linkage with a solidification simulator. The nature of some of the technological challenges which have slowed this development are discussed, including accurate description of complex surfaces and their intersections and the bridging of computer encoded information with NC technologies and with FEM-based simulators for stress and thermal analyses. A recently prepared modular-structured FEM simulation code implemented on a micro computer is described.Construction of a solid geometric model of the casting and rigging and validation of the combination for optimum characteristics of soundness, quality and yield by solidification simulation are I inked as key elements in the foundry of the future. Data base support for this CAD/CAM system is rapidly being developed throughout the world.INTRODUCTIONThe simulation of shaped casting solidification using the digital computer, goes back to at least the early nineteen-sixties when Forsund (1) in Denmark applied the technique to the problems of casting surface quality.Prior to that time, the work of Paschkis and co-workers using the analog computer ranges back to the nineteen-forties, when work sponsored by the AFS Heat Transfer Committee at Columbia University revealed many hitherto unknown or only partly anticipated aspects of casting solidification (2).Three reviews of the various historical aspects of simulation should be referenced. Firstly, the AFS monograph by one of the present writers (RDP) and his colleagues - describing background and later work, again sponsored by the AFS Heat Transfer Committee at the University of Michigan (3). Secondly, a review prepared by Durham and Berry (4) which discusses broad aspects of casting solidification simulation. Thirdly, a review by Erickson (5) which contains an excellent bibliography to 1980. In addition to these papers, the publications lists of the CADCAST project* and the proceedings of the two Engineering Foundation Conferences of Casting and Welding Modeling, published by ASME, are also most notable (6) •"

Jan 1, 1986

By Joseph C. Milbourne

The selection of a suitable nitrate removal process depends on a variety of site-specific chemical and environmental issues. The dominant technologies for nitrate removal include biological denitrification and continuous countercurrent ion exchange. The decision to apply either of these technologies, or both together, depends on the nature of the waste water to be treated. Factors that affect the selection of the biological system include the feed composition and feed temperature. Ion exchange nitrate removal systems are less sensitive to the feed composition but require disposal or destruction of the concentrated pregnant eluate. The paper discusses Tetra&apos;s continuous countercurrent ion exchange technology (CCIXTM) and fixed film biological reactor, Denite°. The treatment of the ion exchange pregnant eluant is also discussed.

Jan 1, 1994

By H. Tan

?Preg-robbing? is the active adsorption of gold from cyanide solution by the ore components. The role of carbonaceous coatings on chalcopyrite surfaces in the preg-robbing of chalcopyrite has been investigated by using pure chalcopyrite and a copper concentrate. Activated carbon and graphite were chosen as representative carbonaceous contaminants. It was found that the carbonaceous coatings enhanced the preg-robbing of chalcopyrite. Activated carbon coating increased gold adsorption onto chalcopyrite to a lager extent, in comparison with graphite coating. In the preg-robbing of the copper concentrate, gold adsorption was increased to larger extent at finer particle sizes and at higher contents of activated carbon or graphite. The preg-robbing of chalcopyrite was reduced or eliminated, depending on the concentrations of free cyanide. However, the gold adsorption on the carbon and graphite coated chalcopyrite could not be avoided even at higher cyanide concentrations, and this adsorption was solely attributed to the carbonaceous coatings. Zeta potential studies indicated that the carbonaceous coatings reduced the negativity of the chalcopyrite surface charge. As shown by SEM analysis, gold not only accumulated at the edges and defect sites, but was also spotted on the smooth surfaces of chalcopyrite with carbon or graphite present. XPS results revealed that gold was strongly reduced on chalcopyrite surfaces, with the sulfide ions of the chalcopyrite being oxidized to elemental sulfur. Diagnostic elution indicated three mechanisms contributing to gold take-up by chalcopyrite, i.e. gold reduction, physical adsorption and chemical adsorption.

Jan 1, 2003

By Klaus-Markus Peters, James G. Hemrick, John Damiano

"Work was performed by Oak Ridge National Laboratory (ORNL), in collaboration with industrial refractory manufacturers, refractory users, and academic institutions, to employ novel refractory systems and techniques to reduce energy consumption of molten material processing vessels found in industries such as aluminum, glass and pulp and paper. The energy savings strategies discussed are achieved through reduction of chemical reactions, elimination of mechanical degradation caused by the service environment, reduction of temperature limitations of materials, and elimination of costly installation and repair needs. Key results of several case studies resulting from US Department of Energy (DOE) funded research programs are discussed with emphasis on applicability of these results to high temperature processing industries.IntroductionRefractory materials are limited in their application by many factors including chemical reactions between the service environment and the refractory material, mechanical degradation of the refractory material by the service environment, temperature limitations on the use of a particular refractory material, and the inability to install or repair the refractory material in a cost effective manner or while the vessel is in service. All of these limitations reduce the energy efficiency of the process as degraded refractory materials lead to loss of process heat (reduced insulation by refractories) and the need for maintenance through repair or replacement of refractory linings.This situation is conceptualized in Figure 1 which shows that when the thickness of the refractory wall is reduced by chemical or mechanical degradation, the heat losses through the wall increase exponentially. The subsequent maintenance to repair such conditions often requires cooling of the furnace or refractory lined vessel which entails loss of energy due to cooling and consumption of energy due to reheating. Additionally, production time and capability are sacrificed.Additionally, in most applications where refractories are used (metal melting furnaces, glass furnaces, steel making furnaces, gasifiers, etc.) wear of the refractory lining is not uniform. Very often, specific areas will wear (become thinner) more rapidly due to exposure to more corrosive or erosive conditions. This concept is illustrated in Figure 2, through the example of excessive metal line corrosion."

Jan 1, 2009

By Linfeng Zhou, Rong Sun, Guanghui Li, Zhiwei Peng, Tao Jiang

Dust, or airborne particulate matter, from metal smelting can be either mechanically or thermally generated and it negatively affects the indoor air quality as well as the fugitive emissions from the plant. The thermally generated dust is often referred to as fume and it is typically generated whenever liquid metal comes into contact with air. For practical reasons, such as vehicle access, etc. it is often difficult to collect 100% of the fume. It is therefore highly desirable to develop processes and optimize operational procedures so that fuming can be kept to a minimum. In this series of experiments, the mechanism of active oxidation and fume formation from liquid silicomanganese under an impinging air jet in the temperature range 1400-1600°C has been explored. Characteristic properties of the fume have been established; particle diameter, shape, size distribution, and elemental composition are reported. The oxidation process is described in terms of vaporization, oxidation and agglomeration. In the boundary layer, two competing mechanisms seem to be operative in parallel: a direct oxidation of Mn vapor, and a two-step oxidation of silicon. The thermodynamic and kinetic conditions governing the two mechanisms are discussed.

Jan 1, 2016

By A. Rohkohl, R. Piillenberg

The QSL plant at "BERZELIUS" Stolberg GmbH in Stolberg, Germany was commissioned in 1990, introducing a new era of lead smelting in the more than 150-year-old history of the lead smelter. The lead smelter in Stolberg has changed its appearance several times during its existence. Therefore, at many locations on the site, old and obsolete buildings and equipment parts can still be seen. They are often located side by side with new modern constructions like the QSL-plant and the mercury removal plant, and reflect the specific contrast between tradition and modern technology. After a brief description of the development of the smelter and its decision to implement the current novel plant, the most recent operating results are reported. Following some modifications to the process and equipment, which had become necessary along with the implementation of the new technology, the plant is in operation today at approximately 30% above its design capacity. These achieved production levels are not restricted by the QSL-reactor but by precedent and subsequent available equipment. The QSL-plant entirely complies with the demands of modern, energy-saving, ecologically compatible lead production technology. Stringent environmental standards are maintained on a continuing basis. The demonstrated viability and flexibility of the overall process permits the operation to adapt quickly to the prevailing economical situation worldwide.

Jan 1, 2000

By D. C. Cupertino

Oxime based solvent extraction provides the user with a selective concentration process for copper prior to electrowinning. The selectivity required is largely for copper(II) over iron(III) and this is achieved by the preferential formation of the square planar copper-oxime complex in the organic phase. The copper/iron selectivity of oximes can however, be altered by modifiers or other types of oximes and may be enhanced in the presence of certain esters. Whilst the oxime based SX processes is important for operations leaching copper from laterite ores, the high selectivity will also be significant in processing streams arising from other leaching regimes which are currently under development, for example leaching of sulfide mineral ores. This paper presents some initial results using Molecular Modelling techniques to further our understanding of the nature of the copper/iron-oxime complexation processes together with some plant studies undertaken at a number of different mine sites investigating selectivity, and other properties, for some modified reagents. Some studies of the interfacial properties of the these systems are reported to explain in part the practical observations.

Jan 1, 1999

By Hong N. Vu, Jitka Jandova

"Gypsum and limestone methods were examined in this study to process zinnwaldite wastes originating from dressing Sn-W ores mined in the Czech Republic. These wastes containing 0.20-0.30% Li and 0.10-0.20% Rb were subjected to magnetic separation to obtain a zinnwaldite concentrate with 1.36% Li and 0.94% Rb. It was observed that processing of the zinnwaldite concentrate with gypsum resulted in almost 96% recovery of Li into aqueous liquors, whilst rubidium extraction was only 25%. At the same time, it is possible to extract almost 92% Li and Rb from the identical zinnwaldite concentrate if the concentrate is processed by limestone method. Lithium carbonate, a final product of both methods was recovered from the refined sulphate solution using K2CO3 as a precipitation agent and/or from unrefined hydroxide solution using gaseous CO2. In the continuation of this study, rubidium will be separated from carbonate solutions after Li2CO3 precipitation as RbAl(SO4)2, an intermediate for Rb2CO3 production. IntroductionLithium is used as an alloying constituent in lightweight alloys, as a heat transfer medium in nuclear reactors and as a component in primary and secondary batteries. With the development of a new generation of electric vehicles, the lithium demand will dramatically grow. Lithium chemicals find extensive application in many industrial branches such as metallurgical, glass, ceramic and pharmaceutical industries. Rubidium compounds are predominantly used in psychiatry and medicine, in magneto-optic modulators, solid-state lasers, phosphors and components of electrolytes for fuel cells. The four most important lithium minerals are amblygonite, spodumene, petalite, and lepidolite. Spodumene LiAlSi2O6 (6.0-7.5% Li2O) and petalite LiAlSi4O10 (3.5-4.5% Li2O) belong to aluminosilcate minerals. Lepidolite (Li.Al)3(Al.Si)4O10(F.OH)2 (3.30-7.74% Li2O), lithium mica, is the most important representative of the mica minerals, a subgroup of the aluminosilicates. It frequently contains 3–5% Rb2O and eventually caesium. Zinnwaldite, which has the general formula K(Li.Al.Fe)3(Al.Si)4O10(F.OH)2 (2-5% Li2O), is regarded as a variety of lepidolite with a high iron content. Commercial amblygonite is a complex phosphate (Li.Na)Al(F.OH)PO4 (up to 9.88% Li2O), however, its deposits have not been commercially exploited because of their small size. Natural brines with a high lithium chloride content are important in the industrial production of lithium [l]"

Jan 1, 2008

By C. D. Chapman

Current regulations regarding the landfill disposal of asbestos containing wastes are inadequate to ensure there are no ground water or airborne emissions. Accordingly, there is growing recognition that asbestos wastes can only be safely disposed of by using techniques that destroy the hazardous fibres. An innovative high-temperature plasma arc technology (The MAGRAM Process) is being developed for the recovery of magnesium metal from asbestos together with supplementary magnesia containing feedstock. The furnace will operate in. open bath mode with aluminium and/or ferrosilicon being employed as reductant. An important advantage of the process is that magnesium vapour within the furnace will be generated close to atmospheric pressure rather than at reduced pressure under which existing processes operate. Thermodynamic modelling work has been undertaken to define the range of slag composition and furnace temperature under which magnesium production at atmospheric pressure is feasible. The effect of slag chemistry, reductant addition, and temperature on product quality and yield have also been investigated and key aspects have been tested on bench scale. A 300 kW pilot plasma furnace unit has been employed for the treatment of calcined asbestos wastes. Aspects of design and operation of the unit are detailed. Acknowledgement: This work is substantially financially supported by the European Communities under the Industrial and Materials Technologies (Brite EuRam H) Research and Development programme.

Jan 1, 1995