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By Seong- Rin Lim

Light-emitting diodes (LEDs) are regarded as environmentally friendly light sources due to their high energy efficiency and lack of mercury content. LEDs are used for a variety of domestic and commercial lighting systems, where they are replacing incandescent and fluorescent lamps at a rapid rate. Incandescent lamps inefficiently consume energy because electricity is mostly converted to heat rather than light. This causes unnecessary environmental impacts and energy consumption associated with power generation and transmission from a life cycle perspective. Although fluorescent lamps are more energy-efficient than incandescent lamps, their disposal at end-of-life presents special challenges because of the presence of toxic mercury. Despite the seemingly apparent advantages of LED, very few studies have rigorously addressed potential environmental consequences of their disposal. Specifically, LEDs are designed with III-V semiconductors that presumably consist of toxic and rare materials, including arsenic, gallium, and indium. We hypothesize that, depending on their concentrations and leachability, these constituents may also contribute to render LEDs as hazardous waste at the end of their useful life.

Jan 1, 2010

By Hui Lu

The structural changes in solutionized AA2618 during natural aging and their effects on subsequent artificial aging were investigated by hardness measurements, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The changes in lattice parameter and hardness during natural aging indicate that copper-enriched clusters form in the earliest stage, followed by the formation of magnesium-enriched clusters and coppermagnesium co-clusters. Prior natural aging consistently weakened the hardening during subsequent artificial aging at 180, 200 and 230 °C but had no effects on artificial aging at 150 °C. The decreased age hardening was attributed to the reversion of small clusters/zones that formed during prior natural aging. The lattice parameter exhibited erratic changes with increasing artificial aging time, reflecting the complex sequence of the reversion and precipitation.

Jan 1, 2006

By C. M. F. Vieira

In the county of Campos dos Goytacazes, north of the State of Rio de Janeiro, Brazil, there is a large production of red ceramic, mainly perforated bricks. A percentage of these bricks are damaged during the firing processing and become a red ceramic waste. This work investigates a possible solution to this environmental problem through the mixture of fired brick wastes, up to 20 wt.%, with clay bodies to produce red ceramics. Cylindrical pressed bodies were fired at temperatures varying from 500 to 1100ºC. After firing, samples were then tested for linear shrinkage, water absorption and mechanical strength. The results showed that brick waste addition did not changed the workability of the clay and that up to 5 wt.% of waste no detrimental effect occurred on the fired properties at all temperatures.

Jan 1, 2010

By A. E. M. Warner

At the Copper Cliff Smelter, Inco Limited has extensive experience in converting primary smelting mattes over a broad range of nickel/copper ratios and compositions. In the past 35 years, technology developments at Inco have reduced the number of Peirce-Smith converters in Nickel/ Bulk (nickel-copper matte) service from 13 to the current 5. This paper will discuss: ? The performance and life of ?stretch? 13.7m shells versus conventional 10.7m converters. ? Process control and information system development from the early 1980?s to view converter aisle status on a continuous basis to the recent central control of the stretch shells. ? Nitrogen cooling of finishing matte from plant testing to implementation in the early 1990?s to replace the dedicated cooling converters. ? The impact on converting of changing the smelter flowsheet in the early 1990?s. ? A current program to develop a converting strategy for the future to address environmental issues and profitability.

Jan 1, 2005

By Tsunehisa Nishimura

Stable operation of the blast furnace needs adequate control of the lower part. To clarify the behavior of the lower part of the blast furnace with accurate consideration of the property of slag and its flow characteristic, a new mathematical model has been developed. Using this model, the effects of the change of operational conditions on the behavior of the lower part of the blast furnace were studied. Further, means to control of the lower part of the blast furnace, especially effective means to maintain adequate temperature, were discussed. And desirable slag property and composition, especially the method to control FeO concentration dripping from the bottom of the cohesive zone to avoid a decrease in temperature of the lower part of the blast furnace was estimated.

Jan 1, 2006

By Xiang Sun

Microwave heating has been used in numerous industrial processes due to its great advantages when compared with conventional heating methods. However, microwave heated products can be affected by non-uniform temperature distribution resulting from the mechanisms of microwave heating. To overcome this problem, a critical step is to have a temperature-time profile. In order to characterize and evaluate microwave heating effects, an accurate temperature measurement is needed. This paper discusses the possibility of applying several temperature measurement techniques in microwave processing. Both contact and non-contact methods are introduced and compared.

Jan 1, 2006

By Orlando C. Gaspar

The textures of the ores, the fine mineral intergrowths, the complex distribution of the deleterious minor elements, and the low base metal contents in some ore types, pose many technological problems to the beneficiation of the volcanogenic massive sulphides occurring in the Iberian Pyrite Belt. In particular fine intergrowths of the base metal sulphides with pyrite impose extremely fine liberation sizes (Kao=15 to 25um). The mineralogical, textural and metallogenic studies have provided an understanding of the distribution of vertical and lateral metal zoning in the ore bodies. Mapping of the ore types, carried out by mine geologists, and the metal zoning patterns computed from data base have shown that ore types are distributed as ore lenses, and that vertical and lateral base metal zoning exists in several orebodies. Since ore processing efficiency is affected by ore textures, and because the same mineral often shows different textural features, a relationship between the textures of the feed ores and those of the middlings must be established for all ore types defined at the deposit scale. For supplying, on time, the information needed for the optimization of the concentration processes, empirical methods of determining the mineralogical and textural characteristics of the several ore types have been developed.

Jan 1, 1995

By I. Gaballah

Jarosite contains up to 15 % of heavy metal compounds 'HMC'. The current waste disposal methods will not be allowed in the near future due to new environmental regulations and pollution risks. For these reasons, thermal treatments of raw or decomposed jarosite, in controlled atmospheres, were investigated. The aim of these treatments is to decontaminate the jarosite and/ or to recover the HMC for recycling. According to physico-chemical characteristics of the samples, the thermal treatments in controlled atmospheres N2, CO+N2 and C12+air lead to the extraction rate that vary from 93 to 98 %. Heavy metal compounds were separated by cooling the gaseous phase. The treatments' residue was almost free from HMC. Between 700 "C and 800 "C, the chlorinating treatment was successful of eliminating more than 97 % of HMC contained in four different samples.

Jan 1, 1999

By Jian Zhang

From the standpoint of quality, surface cracks normally pose more of a problem than internal cracks. Hypo-peritectic (HP) steel grades are well known for their proneness to surface longitudinal cracking (SLC) during continuous casting. This study analyzed the influences of chemical composition, technique parameter and secondary cooling on the surface longitudinal cracks. Based on the optimized the first and secondary cooling zone water distribution in the process of continuous casting, low cooling water distribution at solidification initial stages and uniform cooling at secondary cooling zone were suggested, which can be used to effectively control the surface longitudinal cracks.

Jan 1, 2010

By H. Antrekowitsch

Nowadays, the pyrometallurgical treatment in copper smelters is the common process for the recycling of metals from the electronic scrap. Furthermore the European Directive on the Waste from Electrical and Electronic Equipment (WEEE) and the Directive on the Restriction of Hazardous Substances (RoHS), increase the importance of electronic scrap recycling. Besides these a high amount of plastic and inert components in these materials leads to problems at the processing. An optimisation concerning the internal recovery and the high amount of plastic is necessary to reach the recycling quota of the European directive. The majority of the scrap is treated mechanically in order to separate in a first step plastics from metals, iron from nonferrous metals and harmful substances from valuable materials. But the quality of the different fraction often rather low and further treatment leads to higher costs. Therefore an interaction between mechanical treatment and metallurgical processing should be realised. The Christian Doppler Laboratory for Secondary Metallurgy of Nonferrous Metals at the Institute of Nonferrous Metallurgy at the University of Leoben carried out investigations concerning the optimisation of the metallurgical recycling and the treatment of the input materials especially of printed circuit boards.

Jan 1, 2006

By James P. Bennett

EAF slag chemistry and its control have been recognized as important in producing quality steel at a low price for a number of decades_ EAF steel producers make lime and dolomite additions to furnaces, controlling the CIS ratios and sulfur pickup from the steel. Existing phase diagram data at 1600°C for CaO, MgO, FeO, SiO2, and Al2O3 was used to write a computer model optimizing slag chemistry for slag foaming and reduced refractory wear. The model, its development, and its use in an industrial steelmaking environment will be discussed along with how the model can improve energy efficiency. The importance of EAF mass balance to account for critical materials like Si in scrap and refractory wear using the model will also be emphasized_

Jan 1, 2003

By V. I. Lakshmanan

Crown ethers are gaining importance in separation technology specifically for rare earth elements (REE, La to Lu plus Y) and precious metals (Au, Ag, Pt, Pd, Rh and Ir) due to their specific binding ability, metal complex stability and high extraction efficiency. The selectivity of crown ethers in extraction of these metals depends on different factors, including the cavity diameter and nature of a donor atom of the crown ether, size and charge of the metal ion, diluents and counter ion. Demand for strategic REE and precious metals are consistently increasing in the world while the separation of these metals is most challenging tasks. In this paper, the use of crown ethers in separation of REE and precious metals, reaction mechanisms and simplified process flowsheets will be elucidated. New reagents with high selectivity for the separation of these metals are further expected to produce high purity metals.

By Licheng Zhou

The use of aquatic plants for the removal of heavy metals from wastewater has gained high interest. In this study, batch experiments were conducted to evaluate the adsorption of copper ions in aqueous solution by P. pectinatus L. under various conditions of contact time, initial pH of the solution, metal concentration and adsorbent dosage. The results showed that the maximum adsorption amount of copper ions by P. pectinatus L. was 22.60 mg/g when the initial copper ions concentration was 98.41 mg/L at pH 4.5. The Langmuir and Freundlich models were used to describe the adsorption equilibrium of copper ions on P. pectinatus L. and the adsorption followed the Langmuir isotherm. The adsorption kinetic was well-fitted with pseudo-second-order sorption equations.

Jan 1, 2009

By Joner Oliveira Alves

The aim of this work was to study the use of steelmaking slag as raw material to the production of rock wool and glass wool. Firstly, the chemical composition of the slag was analyzed. These results were used to infer the amount of additives to assemble the charge for the experiments. A laboratory-scale electric furnace was used to melt the mixtures used as charge. The melt material were turned into a water filled recipient, this process was performed in order to impose a fast freezing that is a characteristic of mineral wool production. Finally, with the rest of the melt material it was performed the Herty Viscosity Test. Samples of the produced material were characterized by different analyses. The results found in this research may lead to a technological innovation, because they indicate that the use of steelmaking slag to produce rock wool and glass wool is possible.

Jan 1, 2009

By Xiangjun Zuo

This paper firstly reviewed the state of the art in the recycling of used Printed Wiring Boards (PWB), and then presented part of the authors study on the combustion of PWB powders with and without the addition of catalyst. During the combustion of PWB powders without catalyst addition, there were two obvious exothermic reactions, one at 300-380oC, the other at 450-500oC. With the addition of catalyst during PWB combustion, there were no obvious exothermic reactions, indicating that dehalogenation reactions are not exothermic: The results showed that NaHCO3 and CaCO3 were very efficient to control the emission of Br2 and C6H6, lowering 80% compared to the case without catalyst, Na2CO3 can slightly control the emission of Br2 gas but not for C6H6 gas mission, and NaOH has no any effect of the control of both gases.

Jan 1, 2009

By James P. Bennett

EAF slag chemistry and its control have been recognized as important in producing quality steel at a low price for a number of decades. EAF steel producers make lime and dolomite additions to furnaces, controlling the CIS ratios and sulfur pickup from the steel. Existing phase diagram data at 1600°C for CaO, MgO, FeO, SiO2, and Al2O3 was used to write a computer model optimizing slag chemistry for slag foaming and reduced refractory wear. The model, its development, and its use in an industrial steelmaking environment will be discussed along with how the model can improve energy efficiency. The importance of EAF mass balance to account for critical materials like Si in scrap and refractory wear using the model will also be emphasized.

Jan 1, 2003

By Daniel Bennett

There are few methods currently applied towards on-line bulk mineralogical analysis. Yet on-line knowledge of process mineralogy could potentially provide large benefits, such as increased extraction efficiency or resource optimization. The work described in this paper involves the development of radio frequency methods for bulk mineralogical analysis. Some resonances that occur in the radio frequency spectrum are mineral specific, and potentially allow quantitative estimation of mineralogy in an ore stream. Results will be presented on the specific detection of chalcopyrite. Initial quantitative measurements investigating matrix effects have indicated the feasibility of on-line mineralogical estimation using radio frequency techniques.

Jan 1, 2006

By José Carlos D?Abreu

The Tecnored process is a new ironmaking technology, developed on a unique approach that combined empirical and theoretical knowledge backed by extensive tests carried out in a dedicated pilot-plant and with close support of universities and research centers. Campaigns in the pilot-plant focused on operate different reactors of different sizes, including a full size slice of the industrial furnace. This approach provided actual conditions to develop the main features of the process such as the internal dimensions, raceway pattern, thermal and gaseous profiles, etc, besides provide reliable data to feed and calibrate a specific mathematical process modeling. This paper presents the first computer model used by the Tecnored technical staff, focusing the behavior of a self reducing agglomerate in the upper shaft of the furnace (zone of solid state reduction). Some results of this model are given and discussed.

Jan 1, 2006

By Sergio N. Monteiro

Wastes generated by our society and the question on how to dispose them is, nowadays, a relevant matter of concern. The objective of the present work was to characterize the technical properties of composites made of discarded jute sackcloth with its coarse wove fabric, serving as reinforcement phase, and polyethylene wastes collected from city dumps, as continuous matrix. Different amounts, up to 30 wt.% of jute plain weave, fabric were press molded at 160°Ctogether with sieved polyethylene particles. The resulting composites displayed mechanical properties that could compete with those of low-density wooden board. Both by presenting a solution to, otherwise, disposed wastes and by helping to prevent deforestation, the investigated composite may be regarded as an environmentally correct material.

Jan 1, 2006

By S. q. Honingh, G. Van Weert

Currently produced zinc-enriched blast furnace dust is stored on site at CORUS IJmuiden. To end this practise, a research program was started in 1996. Four technologies were studied: oxidative autoclave leaching in a chloride medium, fluid bed pyrohydrochloridisation (pyrohydrolysis) to yield lead-zinc-free (hematite) calcine, EAF (plasma) smelting/zinc fuming, and incorporation of the dust in 'iron foundry cupola charges. All aim to remove zinc and lead, recycle the iron residue internally, and produce a saleable zinc-lead product.

Jan 1, 2000