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By David E. Jones

In any manufacturing process, the generation of secondary, associated or waste products along with the primary product is inevitable. Today there is great emphasis on the concept of waste minimisation. As part of that overall strategy, the search .for markets for these materials formally regarded as wastes, can mean the development of whole new industries. This paper examines some of the work necessary to develop recycling and markets for associated products with particular reference to iron and steelmaking slags.

Jan 1, 1994

By Jing Zhang, Chenguang Bai, Fusheng Pan

"The microstructure and hot deformation behaviour of an Er-modified Mg-Zn-Ai alloy were evaluated. The results showed that the addition of rare-earth Er changed the morphology of the quasi-continuous grain boundary networked eutectic compound to globular particles. Moreover, a self-strengthening effect was identified for the alloy, which determined its deformation behavior. After hot extrusion, the yield strength and elongation to failure of the Mg-Zn-AI-Re alloy at 200°C were increased by 105% and 120%, respectively, due to an emerged dynamic precipitation strengthening mechanism.IntroductionMagnesium alloys are attracting increasing attention for applications in automobile, electronic devices and hand tools for weight reduction and higher fuel efficiency, because of their lightweight and a high specific strength. However, application of Mg is still very limited. The largest applications are still those non load-bearing castings used at room temperature, such as box case, housing, and covering. One of the main reasons is the inadequate absolute strength both at room temperature and elevated temperatures (> 100°C) of the commercially used AZ, AM series alloys, due to the incoherent interface between the secondary phase y-Mg17AI12 and Mg matrix, as well as the low thermal-stability of the y phase [1]. Besides, the heat-resistant magnesium alloys which contain rare earth (Re) as the main alloying element are very expensive. The other reason is their poor deformability. The key solution is therefore to develop low-cost heat -resistant wrought alloys."

Jan 1, 2012

By Mark Samonds

"Manufacturing processes which involve liquid to solid and solid state transformations in metals encompass a wide variety of physical phenomena. The past twenty years have seen a steady evolution in the complexity and scope of numerical models of these processes, beginning with thermal analyses without phase change. Recently, a few software packages have become available which have true multi-physics capabilities. This permits the treatment of thermal, fluids, stress, electromagnetic, chemical reaction and microstructure development aspects altogether in a fully coupled simulation. This paper will consider various aspects of these types of models.Coupled thermal and fluid flow analyses of continuous castings have been around for fifteen years. Coupled thermal and free surface fluid flow simulations of shape castings have been available for ten years, including view factor radiation models for investment castings. Only recently, however, have fully coupled thermal, fluid, and stress analyses become practical. This implies the reverse coupling of the mechanical deformations to the solution of the energy and momentum equations through modification to the interface heat transfer coefficients and the fluid domain geometry. This has been implemented with a combined eulerian-lagrangian finite element method. Appropriate mechanical constitutive models will also be discussed.Many types of defects need to be predicted in casting processes. Those related to stress include hot tearing, hot cracking, part distortion, and thermal fatigue in dies. Macroporosity, microporosity, and microsegregation are determined by the solidification behavior and microstructure development in a casting. In particular, microporosity is influenced by dissolved gases, the morphology of the mushy zone, the liquid to solid density change, and the local pressure conditions. Macrosegregation is caused by the partitioning of solutes during. solidification and subsequent thermo-solutal convection. An additional transport equation is required for each solute that is being tracked. Computational thermodynamics is being incorporated into these types of analyses to determine transformation temperatures, partition coefficients, densities, and enthalpies. In combination, the microstructure and microporosity models can frequently predict a variety of mechanical models, such as yield strength, tensile strength, and elongation."

Jan 1, 2001

By Isabela Leao Amaral da Silva, Alice Barreto Bevitori, Frederico Muylaert Margem, Victor Bastos da Silva, Sergio Neves Monteiro, Artur Camposo Pereira

"The jute fiber is one of the most rigid natural lignocellulosic fibers, which has since the last decade been investigated as possible reinforcement for polymeric composites. In the present work, the tensile properties of DGEBA/TETA epoxy composites reinforced with jute fibers with different diameters were investigated. Composites with volume fractions up to 30% of continuous and aligned jute fibers were tensile tested at room temperature to evaluate the ultimate strength, elastic modulus and total strain. For each volume fraction, separated fibers with smaller larger diameters were tested. The results indicated that the tensile properties tend to improve with increasing volume fraction of the thinnest jute fibers. The role played by the fiber/matrix interaction was analyzed by scanning electron microscopy.IntroductionThe interest of this research is to develop composites with epoxy resin matrix reinforced with continuous and aligned jute fibers, for applications in various industries, including construction and automotive industry. Conflicts related to the use of non-renewable forms of energy are increasing the interest to enter the market to replace natural materials, synthetic materials synthetics have a higher power consumption in its manufacture [ 1-4].Therefore, applications of natural lignocellulosic fibers obtained from cellulose-based plants are receiving increased attention as an alternative to replace more environmentally correct nonrecyclable materials, energy intensive and glass fiber composites in [5-6]. The use of composites reinforced with natural fibers is a reflection of the concerns with environmental issues such as pollution caused by waste that is not biodegradable or cannot be incinerated and climate change due to C02 emissions associated with the processes of intensive energy and also motivates this work to develop self-sustaining, since natural fibers generate a source of income, especially in developing countries, where most originate, encouraging the cultivation of non-food agriculture [7-9]. Additionally, it is worth also remembering that these fibers come from renewable sources, in addition to being abundant, inexpensive and have a relevant set of mechanical properties [10]."

Jan 1, 2013

By Mala Nath, Atjit Mallick, Asheesh Kumar

"The present research work is aimed to focus on the development of chemically stable light weight microporous carbonaceous material, such as activated charcoal incorporated either with titanium n-butoxide, titanium diisopropoxide bis(2,4-pentanedionate), vanadium 2,4-pentane-dionate or zinc 2,4-pentanedionate having varying wt% of the metal (2-8%) using ethanol as solvent at 40--50 oC followed by calcinations at 100, 150 and 200 cC, except the samples with titanium diisopropoxide bis(2,4-pentanedionate) which are calcinated at 80 oC. Atomic absorption studies along with FESEM revealed that the maximum incorporation of metals (Zn, V and Ti) in activated charcoal was observed with 4 wt% of zinc 2,4-pentanedionate calcinated at 150 oC , 4 wt% of vanadium 2,4-pentanedionate at 100 oC, 2 wt% of titanium n-butoxide at 100 oC and 2 wt% of titanium diisopropoxide bis(2,4-pentanedionate) at 80 oC, and equilibration time of 20-24 h was used in each case. Hydrogen sorption behavior in these carbonaceous materials has also been studied at 77.4 K and low pressure up to I bar. The highest hydrogen uptake obtained was 1.45 wt% (164.5 cm3 (STP)/g at P/Po = 1.0) for activated charcoal incorporated with 4 wt% of zinc 2,4-pentanedionate calcinated at 150 oC.IntroductionTwo of the major challenges for humanity in the next twenty years are the shrinking availability of fossil fuels, the global warming and potential climate changes that result from their ever-increasing use. So it is necessary to fmd an energy source that is convenient, flexible and controllable. One possible solution to these problems is to use an energy carrier such as hydrogen, and ways to produce and store hydrogen in electric power plants and vehicles. Hydrogen storage is the bottleneck for the breakthrough of hydrogen as energy carrier in automotive applications [1]."

Jan 1, 2012

By Xinli Wang, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Byoung-Gon Kim

"The microwave dielectric properties of silicon dioxide at frequencies of 915 and 2450 MHz were characterized in the temperature range of 24 to approximately 1000 °C using the cavity perturbation technique. It is shown that the relative dielectric constant of silicon dioxide at both frequencies remains almost unchanged below 500 °C, above which there is a slight increase of 2%. The relative dielectric loss factor of silicon dioxide exhibits a strong temperature dependence above 500 °C and increases by approximately 7 and 5 times at 915 and 2450 MHz, respectively. The substantial increase in the relative dielectric loss factor is mainly attributed to the enhanced dielectric polarization and accelerated electrical transport in silicon dioxide at elevated temperatures.IntroductionSilicon dioxide (Si02) is usually considered a microwave transparent material due to its poor absorption capability at room temperature [1]. This characteristic has led to various applications of silicon dioxide in microwave processing of materials and communication. For instance, Si02 has been used to produce sample holders for microwave heating and substrates for electronic devices [2,3]. These applications generally require the material to withstand high temperatures under microwave irradiation. This indicates that microwave absorption capabilities of silicon dioxide at elevated temperatures are also important for its utilization.The microwave absorption capability of Si02 can be determined based on dielectric characterization (permittivity measurement) of the material at commonly used microwave frequencies, 915 and 2450 MHz, in a broad temperature range. To date, however, no detailed work on the dielectric properties (permittivity) of silicon dioxide at high temperatures has been reported. The present work is aimed to study the dielectric properties of silicon dioxide from room temperature to approximately 1000 °C at 915 and 2450 MHz. The results show that the permittivity of silicon dioxide has a strong temperature dependence above 500 °C, suggesting a substantial increase in its microwave absorption capability."

Jan 1, 2013

By Andrew Shabalin, Vladimir Skorohodov, Svetlana Babaeva, ?lga Makovskaya

"At processing of some kinds of wastes (electronic scrap, secondary materials, spent nuclear fuel) in nitric acid solutions, and also in technology of silver refining, the significant amounts of palladium and platinum passes into a solution. The ion-exchange concentration of palladium and platinum in nitric acid solutions (5-500/dm3) are investigated. More than 30 various classes of ionites are tested. The most chemically resistance resins at the given conditions are identified. It is shown, that the maximum sorptive capacity to studied metals at high acidity the complexing, synthetic and inorganic sorbents possess. To definition of platinum metals sorption optimum conditions the kinetics is studied, isotherms of a sorption at various parameters from nitrate solutions are obtained. The conditions of the platinum and a palladium desorption from the pregnant sorbents and its regeneration with the subsequent reuse of materials were defined. The raw materials containing precious metals have very diverse composition and physical properties. Commonly the materials are processed by hydrometallurgical way. If gold or PGMs there are in raw materials to its opening hydrochloric acid solutions are applied. As an oxidizer nitric acid, hydrogen peroxide, gaseous chlorine, etc are used. Nevertheless, at processing of argentiferous materials and preliminary treatment of a waste including the spent nuclear fuel, nitric acid solutions are often used and the specified metals in some extent pass into solution [1]. Therefore selective extraction of PGMs from nitrate solutions is an actual problem. In the present work the ion-exchange concentrations of palladium and platinum in nitric acid solutions (5-500 g/dm3) are investigated. At the testing more than 30 various classes of ionites the most chemically resistance resins at the given conditions are identified. These resins are synthesized on the base of polyacrylate, styrene-divinylbenzene and vinylpyridine. For a selection of the most effective resin among what are made in Russia and overseas, a number of ionites with various functional groups were studied. Influence of functional groups type on a PGM sorption is shown for extraction of a palladium as an example (table 1). The presented data shows, that palladium concentration in a phase of ionites depends on sorbent type. If the increasing of solution acidity essentially reduces palladium sorption by sulfonic cation-exchange resins (KU-2×8) than its sorption by strongly basic anionites is approximately equal. Intermediate position is occupied by complexing sorbents. The latter (AN-31, SN-3, ANKB-35, Lewatit TP 207, Purolite S 930) are the most effective for extraction of PGMs from nitrate solutions from the point of view of capacity value. According to [2], solution behavior of Pt (II) and Pd (II) are similar. As is known from coordination chemistry, ligand environment of the metal ions substantially impacts to character of electronic spectra. The figure 1 shows the results of measurements of optical density of platinum bearing solutions with various concentration of nitric acid at ?=400 nanometers"

Jan 1, 2008

By Rajesh K. Mishra

In secondary precious metals refining, the feed to the plant itself is a waste generated in manufacturing processes. Constant changes in manufacturing processes produce ever changing feed materials to the secondary PGM (platinum Group Metals) refineries. After extracting the precious metals, secondary wastes are generated. The discharge of effluent is dictated by both the PGM losses in wastes and the regulatory mandates. This paper will discuss some. of the conventional as well as some newer approaches to face both the challenges.

Jan 1, 1995

By Yang Tian-zu

Sodium pyroantimonate which is widely used as the clarifier in the glass industry and as the synergist in anti-flaming industry respectively has a production history of about 30 years in China. At present there is the production capacity of about 20,000 tons per year in China and China is chief producer of sodium pyroantimonate. In this work the production processes adopted by the producers of China, the operation conditions and the product qualities of sodium pyroantimonate prepared by different preparation methods have been summarized, and on the basis of comparing the advantages and disadvantages for each process the most advanced method - the air-oxidation method was introduced in detail. The production processes of sodium pyroantimonate mainly include the method of oxidation by sodium nitrate, the oxidation method of hydrogen peroxide, the potash salt method, the chlorination method and the air-oxidation method etc. The method of oxidation by sodium nitrate in which the crude antimony oxide, sodium carbonate and sodium nitrate are separately used as the raw material, the flux agent and the oxidant, has the advantage of short and simple technological process, but low grade quality of sodium pyroantimonate and bringing about serious environmental pollution are the disadvantages and this method has been substituted by other methods. Sodium pyroantimonate can be directly prepared by the hydrogen peroxide oxidation method with the advantages of simple technological process, high grade quality of the product and little environmental pollution. High grade quality of sodium pyroantimonate can be also synthesized by the potash salt method, in which industrial antimony white, the hydrogen peroxide, potassium hydroxide and sodium hydroxide are applied as the starting material. The disadvantages of these two preparation methods are high production cost and high requirements on the raw materials. The chlorination method with the crude antimony oxide, hydrochloric acid and chlorine as the raw material has the advantages of low production cost and high grade quality of the product. However complex process, high requirement of anti-corrosion for the equipments and producing plenty of waste water limit its application. The air-oxidation method with stibnite/jamesonite concentrate, sodium sulfide, and sodium hydroxide as the raw material and atmosphere as the oxidant is a newly developed method and its advantages are low production cost and the complex raw material can be treated by this method and its disadvantage is that the quality of sodium pyroantimonate is lower than that prepared by the oxidation method of hydrogen peroxide and the potash salt method.

Jan 1, 2006

By Nicholas S. Lynn

"A new process has been developed to bioleach refractory gold ores to expose the precious metal values using Thiobacillus ferrooxidans bacteria.The ore is hosted in a limestone rock with secondary replacement of carbonaceous and pyritic minerals. Crushing, stacking, bioleaching, rinsing and neutralization have been completed in a 45-day total time cycle. The use of sulfuric acid operation, and concentrated Thiobacillus ferrooxidans population allows the short bioleaching cycle.The ore is then processed using conventional Carbon-In-Leach Cyanide recovery techniques.ABSTRACT ONLY"

Jan 1, 1997

By Raymond PoIick

The Demag Electric Slag Cleaning Furnace installed at the Asarco Smelter in Hayden Arizona is one of the few rectangular electric furnaces now operating. The long transition times from charge to tap allow exceptionally clean skims (high recovery); however, the furnace design is complex. Additional Asarco requirements for rapid installation and commissioning further complicated the design. When operating and wear effects accumulated after two years of use, steps were taken to rebuild the furnace with enhanced durability based on the design parameters experience in actual use.

Jan 1, 1993

By F. J. Tavera

A study on the electro kinetics of lead carbonate, silica, and alumina, in aqueous media was carried out at different pH values. The behavior of potential was determined for these species in the pH range between 3 and 12. Homocoagulation of lead carbonate in aqueous media is analyzed at its isoelectrical point. Lead carbonate heterocoagulation is analyzed with silica, alumina, and silica ? alumina mixtures at low pH values. The experimental results are considered for their possible application to treat residual water polluted with lead.

Jan 1, 2006

By Toshihide Ito, Jie Liu, Takashi Nishiyama

"Human society evolved from an agricultural to industrial and, subsequently, to a service society. As the resource requirements for each stage of this development differ, trends of metal and energy consumption are related to shifts in society. The increase pattern of supplemental energy is similar to that of mineral production throughout the world. Low positive and stable long-term increasing occurred before 1950, whereas they increased quickly after 1950, especially between 1950 and 1973. A substantial decline in· the growth of energy and mineral production began in 1973 and lasted until the early 1980s. Production of energy resources has recently begun to increase again at a high growth rate in the world. Observing the consumption trends of energy and key metals, it is clarified that increasing patterns can be thought in three stages.IntroductionHuman society evolved from an agricultural to industrial and, subsequently, to a service society. As the resource requirements for each stage of this development differ, trends of metal and energy consumption are related to shifts in society [1-3]. Humphreys [4] described that both the non-ferrous metal consumption and the construction material consumption showed a similar trend dropping markedly in the UK over the period 1960-1992. On the other hand, per GDP (Gross Domestic Product) consumption, that is, the intensity of use of construction materials has declined sharply over the past 30 years, more so than the intensity of metal use in the USA [5]. Nishiyama [6] observed that increase pattern of supplemental energy is similar to that of mineral production throughout the world."

Jan 1, 2000

By Mahmoud A. Rabah

"In this work, metal values were prepared from used beverage cans. The cans are made of aluminum and minor alloying metals and printed with a multi-color printing ink. A method has been investigated to remove the printed coating using organic solvents or by sand blasting technique in a rotating drum. Metal values of the cleaned cans are prepared applying combined hydro and pyrometallurgical treatments. Factors affecting the efficiency of the suggested method have been studied.The results show that the extent of removal of the printing coating is successfully performed with recyclable methyl ethyl ketone I dimethyl formarnide mixture. With sand blasting, it proceeds regularly with the inner diameter, the rotation speed of the drum, the size of the sand grains and temperature. The removed coating is stripped with the same solvent. Metal alloy(s) are prepared in two ways. In the first way, the cans are pressed into solid blocks using hydraulic press before melting at temperatures up to 1000°C using borax-sodium chloride salt mixture as a flux. The quality of the metal obtained is a function of the salt and temperature. The slag so formed was leached with mineral acid solutions. In the second way, the used beverage cans are directly dissolved in mineral acids whereby different metal values are selectively precipitated. The undissolved part is fused with sodium carbonate at 800°C and processed in the same manner. Results were explained in the light of the thermodynamic properties of the species involved."

Jan 1, 2000

By David Langberg

Recovery of dissolved copper from discard slags is a critical consideration affecting the economics of copper smelting. Slag cleaning is frequently carried out in electric furnaces, however reduction by injection of natural gas in a holding furnace may offer a lower cost alternative in some circumstances. As the residence time of the injected gas is short, the factors controlling the rate of reduction need to be clarified in order to optimise the design of the slag cleaning furnace. A series of medium scale (200 kg) reduction tests to investigate the rate of reduction of copper-containing slags by injection of natural gas-nitrogen mixtures between 1150-1250C was carried out by CSIRO Minerals. The composition of the gas in the top-space of the reactor was found to be significantly more reducing than the slag, indicating that thermodynamic equilibrium was not established between the slag and the gas in the bubble plume. An apparent first order rate law was observed between the rate of oxygen elimination from the bath and the magnetite concentration of the bath. The dissolved copper concentration was closely correlated with the oxygen potential of the slag, suggesting a partial equilibrium between the dissolved components of the slag. The utilisation efficiency of the natural gas decreased as the natural gas flow rate was increased. The results of the tests tend to indicate that the rate is controlled by a mixed reaction kinetics/ mass transport mechanism. The work was supported by Xstrata Copper ? Mt Isa Mines.

Jan 1, 2006

By Natasa Mitevska

In the world, as well as in Republic of Serbia, conventional ore reserves are almost exhausted, so the problem of their shortage is more and more expressed. On the other side, there are many locations with significant reserves of polymetallic ores which present huge potential but cannot be classically processed. Each of these classes of materials has particular mineralogical characteristics which affect their processing. Because of that it is necessary to develop particular technology for each unconventional ore in order to extract valuable elements. The aim of investigation was to define technology for complex processing of the Blagojev Kamen sulfide concentrate by pyrometallurgical procedure in order to valorize valuable non-ferrous and precious metals present, and profit with absolute respect of environmental protection laws. The complex composition of the Blagojev Kamen sulfide concentrate with high content of non-ferrous (15.59% Pb, 9.05% Zn, 2.37% Cu) and precious (697 g/t Au and 744 g/t Ag) metals was the main factor for technological procedure and collector selection. Laboratory investigations are done in four series according to technological scheme: oxidizing roasting, charge preparation (flux addition and agglomeration), smelting under reducing conditions, lead bullion refining, Dore metal refining to final products. It is concluded that precious metals are concentrated in lead bullion (up to 97.95% of gold and 93.37% of silver), which has similar composition to lead bullion produced in lead metallurgy. In this case, simplified technology is used for lead bullion processing because of low content of arsenic, bismuth, etc.

Jan 1, 2006

By Thomas Niehoff

"Oxyfuel combustion systems are state of the art for many melting operations. Airfuel systems have been stepwise modified to oxygen enrichment, oxygen lancing and oxyfuel. Every change of the melting process will have consequences with regards to emissions and energy usage. The uniqueness of many operations requires unique skills to resolve potential issues. This paper will give some examples of how airfuel systems can successfully be converted to oxyfuel.IntroductionOxyfuel technology – meaning the combustion of fossil fuels such as natural gas, oil or coal with technical oxygen instead of air for industrial melting or heating processes is widely used in many industries these days. Even though oxygen production, storage and handling has been state of the art for decades other opinions exist. Often oxyfuel is regarded with fear and potential hazards like: “Oxygen makes the process too hot.”, “Oxygen will melt away the refractory.”, Liquid oxygen is dangerous.”, “Oxygen will cause explosions.”, ……etc.Typically a more detailed discussion about a specific industrial process and how oxygen can be applied in a safe and economic way the seeming issues go away."

Jan 1, 2010

By O. G. Yeremin

The Joint Venture "Inter-S" jointly with the Gintsvetmet Institute have developed a technology for manufacturing of sulphoconcrete and sulphoasphalt. The sulphoconcrete manufacturing technology comprises preliminary production of modified sulphur, which is blended in liquid form at a temperature of 120°C with an inert material preheated to the same temperature. The second promising area for the use of sulphur is partial substitution of modified sulphur for more expensive bitumen. The sulphoasphalt manufacturing process comprises preliminary production of a sulphur and bitumen mixture with a sulphur content of 30% to 40%, which is then blended with inert materials using conventional techniques. Sulphoasphalt manufactured at a full-scale plant meets all requirements set to its strength properties for road paving. Technology has been developed for production of high-purity sulphur based on rectification of liquid sulphur in a packed column. A commercial-scale plant with a capacity of up to 15 tonnes per year for production of sulphur with an impurities level of about 110-6 % by mass has been put into operation.

Jan 1, 2006

By M. I. Kalashnikova

Gipronickel Institute has developed the technology of treatment of difficult to concentrate sulphide Pb-Zn concentrates (Zn-19,9%, Pb-8,4%, Cu-0,34%, Fe-8,8%, Ba-6,8%, S-18,7%, Ag-106 g/tonne). The technology consists of pressure leaching, impurity removal from leaching solution, electrowinning and Pb-Ag containing cake treatment. Despite low zinc content in initial concen-trate the technology allows production of solution which is suitable, after standard procedure of impurity removal, for electrowinning with production of zinc grade SHG. Comparing to the standard technologies the flowsheet developed provides the lesser expenses per zinc unit because of decreasing of liquid to solid ratio at pressure leaching stage. The initial concentrate is characterized along with low content of principal metals by high con-tent of barite, which makes flotation of pressure leaching residue more difficult. That is why in this case the hydrometallurgical treatment was chosen. At optimal parameters of chloride leach-ing found during laboratory experiments the principal components extraction was 99.5% for Pb and up to 92% for Ag.

Jan 1, 2006

By Gerardo R. Alvear

The ability to efficiently remove impurities contained in concentrates is a key point to consider when selecting copper smelting technology for new plants or modernisation projects. Volatilisation of impurities such As and Sb should occur as early as possible in the process, and preferably in the smelting furnace, so that they do not impact on downstream unit operations. The ISASMELTTM process has been demonstrated to remove impurities efficiently, through high levels of volatilisation. This behaviour is promoted by attributes of the process such as the strong bath agitation, and the flexible nature of the process design, allowing the operator to choose the optimal matte grade for impurity partitioning, and the positive effect of the moisture content in the feed. This paper presents the distribution of minor elements in the copper ISASMELTTM furnace. Distribution impurities of As, Sb, Pb, Zn and Co observed in the ISASMELTTM furnace at Mount Isa Smelter are reported. Then, based on plant results and thermodynamic considerations, the potential application of ISASMELTTM technology for processing complex concentrates is discussed.

Jan 1, 2006