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By Christian Ludwig, Virginie Silberstein, Rizlan Bernier-Latmani, Simona Regenspurg

"Residues from waste incineration (bottom ashes) form large amounts of heavy metal-rich waste. Theoretically, heating and the addition of chloride to the ashes could remove these metals by formation of volatile metal chlorides. The remaining heavy metal-poor ashes could be used, for example, as cement additives. In the proposed process of our study we used bypass dust from the cement industry as chloride additives to the bottom ashes. We aim to determine experimentally the optimal conditions to remove heavy metals from ashes and to simulate this process by thermo- chemical modeling. In our experiment we investigate heavy metal flows by heating of differently composed mixtures of bottoms ash and bypass dust in dependence of different furnace temperatures (500-1200 °C). Furthermore, we investigate the reactivity (leaching characteristic) of the resulting product in order to predict if secondary residues can be landfilled in agreement to Swiss regulations for inert materials.IntroductionThe incineration of garbage is generally considered as the most environmentally friendly method for the reduction of municipal solid waste. This is because, compared to traditional storage of waste on landfills, incineration produces less greenhouse gases and destroys toxic organic compounds. The released exothermic energy can be recuperated and the residues from the combustion chamber (bottom ash) are strongly reduced in volume. However, they still form about 600 kt of waste per year in Switzerland, which needs to be landfilled. However, these residues could be potentially used as construction materials after mechanically recovering ferrous and non-ferrous metals. However, the resulting ashes (discharged dry or wet) still contain increased amount of heavy metals (exceeding state regulation) requiring them to be finally deposed on a hazardous waste site. A thermal treatment of these ashes could enable both, to separate and recuperate the remaining heavy metals and an inorganic heavy-metal poor material. The evaporation of metals depends on temperature and can be lowered by addition of chlorides, which would lower the boiling point of most metals by formation of metal chlorides (table 1)."

Jan 1, 2008

By Kliment Y. Hakobyan

A new technology for treating molybdenum sulfide concentrates has been developed. It includes roasting the concentrate in a special regime with water vapor, cooling and neutralizing exit gas, oxidation roasting of rhenium containing MoO2, and the extraction of rhenium from exit gases. This technology allows economically efficient and environmentally safe processing of molybdenum concentrates: The degree of molybdenum extraction is 98.8%, rhenium-90%, sulphur-98.4%. The technology also ensures high extents of extraction of selenium and tellurium as well as the fixation of sulfur in the form of sodium sulfide or elemental sulfur.

Jan 1, 2006

By Yoshiaki Suzuki

In 1996, Saganoseki smelter & refinery successfully shifted to a single flash smelting furnace operation and increased the copper production capacity to 450,000mtpy in 1998. As the next step, Saganoseki planned to further increase the productivity in the smelting process. Applying the latest technology and carrying out technological innovations the throughput of the flash smelting furnace has been increased to 195 tons per hour and the matte grade has been raised to 68%. In 2005, six PS converters have been successfully consolidated into four by maintaining the production capacity. This paper introduces recent operation conditions and results of implementation of technological improvements.

Jan 1, 2006

By P. G. West-Sells

Recovery of gold from thiosulfate leachates can be accomplished by adsorption of the gold thiosulfate complex by a strong base resin. Two of the most significant impurities that can decrease this gold adsorption are tetrathionate and trithionate, which are produced as oxidation products of thiosulfate during gold leaching. This paper investigates gold adsorption on a strong base resin (Purolite A500C) as a function of the concentration of these impurities. It is shown that concentrations of tetrathionate and trithionate as low as 150 mg/L can decrease gold loading by an order of magnitude, and that of the two ions, tetrathionate has a stronger detrimental effect. The resin and solution gold concentration profiles were successfully fit using a Freundlich isotherm, which further shows the strong effect of tetrathionate. To counteract the decrease in gold adsorption by tetrathionate, a novel process was proposed. Sulfite was added to the solution to oxidize tetrathionate to trithionate, and a nitrogen blanket was added to ensure that no further oxidation of thiosulfate could take place. It is shown that by incorporating this process, gold adsorption was doubled from both synthetic and real gold thiosulfate leachates.

Jan 1, 2003

By M. Huang

A conductivity-based sensor for on-line measurement of free acid was recently built. This sensor is suitable for high ionic strength solutions and its corrosion-free operation is based on induction currents. It has been tested against literature data and measurements made using a previous developed contact-type conductivity cell, with an average difference within 1%. The electrical conductivities of H2SO4?H2O, H2SO4?MgSO4?H2O and NaCl?Laterite-H2Osolutions at temperatures up to 250 °C were discussed. It was found that the solution conductivity depends on various factors, such as the electrolyte concentrations, the type of electrolytes, temperature and the amount of dispersions. A semi-empirical model was developed to account for all the factors discussed. This model was further tested on actual process solutions from the hydrometallurgy of nickel where sulphuric acid solutions containing a variety of metal sulphates and solids. The average difference between the estimated acid concentration from this model and the one from titration was generally less than 5%, which is excellent for industrial applications.

Jan 1, 2006

By J. Antonio Barrera-Godinez, S. E. James, J. Sun

The solvent extraction separation of iron from a zinc sulfate medium using DEHPA was investigated. After loading, the ferric ions were reduced in the organic phase using metallic zinc. The ferrous ions produced could be easily stripped into a sulfate solution with pH values in the range of 1.4 to 2.0. The small, laboratory scale pilot system used in this study allowed for continuous cycling of the organic and strip aqueous solutions. It was possible to establish and evaluate a series of steady state conditions under selected operating paiameters. The effects of processing parameters such as solution chemistry, flow rates, zinc metal loading and pH on iron recovery and efficiency were also evaluated. Under proper conditions, it was possible to remove about 5 g/L iron from the organic phase in one stage and to produce a concentrated iron sulfate strip solution containing ferrous ion concentrations in the range of 90 to 130 g/L. Preliminary feasibility tests were also made on electrowinning metallic iron from the strip solutions and crystallizing ferrous sulfate as a means of making a marketable iron product.

Jan 1, 2000

By C. Niedersberg, M. K. Almeida, R. M. C. Santana, V. G. Dalenogore

"The major source of environmental pollution in urban areas is the transport sector and its impact on human health and the greenhouse is preoccupying. In many works of literature is monitored the pollutants in urban cities, however in specific areas such as universities, they are scarce. Therefore, the aim of this work is to monitorate the gaseous pollutans in a bus terminal at Santa Cruz do Sul University-UNISC and to develop a control framework of the air quality. Six points were selected for monitoring, being one of them inside a bus. The monitoring of CO, HC and CO2 were carried out on arrival and departure of the bus. Preliminary results conducted in a day of spring showed that the most critical condition was during the night shift, where the concentration of CO (200 ppm) was the highest, caused by the vehicles increase, due to the larger number of students.IntroductionAccording to Mascarenhas et al, 2005, air pollutants are responsible for various effects on vegetation, ecosystems and is recognized as one of major public health problems of today, with harmful effect on humans even at levels considered safe by Brazilian legislation.There are numerous scientific papers linking air pollution with respiratory problems, cardiovascular which hinder the daily life because many of these diseases are chronic and may even lead to death, as was noted by Brook et al, 2004.There is a significant increase in the last decades of emissions to air resulting mainly from human activities. Already being observed the relationship of these emissions with the change in global climate, IPCC, 1995.They are a multitude of pollutants from the atmosphere, and its sources and its effects. The effect of Greenhouse gases (GHG), representing less than 1% of the gases in the atmosphere, controlling the flow of energy in the atmosphere. The increase in emissions of greenhouse gases is affecting the Earth's average temperature, which depends on the balance between these flows, in particular the flow of solar radiation reaching the surface and the flow of infrared radiation sent into space.One of the main greenhouse gases to this imbalance is the gas methane (CH4). Methane is produced by anaerobic decomposition of organic substances, through the action of bacteria metanogenic conditions that require highly reduced to its growth. This gas is released into the atmosphere mainly by transport diffusive by aerenchyma (vascular tissue) plant and also by diffusion through the water slide. (Bont et al., 1978)."

Jan 1, 2008

By Robert E. Brown

Magnesium recycling has been used to recover both new scrap and old scrap. It was used extensively in Germany during WWII to expand the magnesium supply. There were a large number of magnesium recyclers in the US who got their start smelting old scrap, old airplanes and old waste dumps from the WWII build up. As the world magnesium industry dwindled, only a few companies were left that did magnesium recycling as a primary business. The sand foundries tended to recycle of their production scrap in their melting furnaces. Even the original die casters tended to put scrap directly back into melting furnaces at the die casting machines. As high purity alloys were developed and the use of die castings in automotive work increased, the tendency was to let the magnesium recyclers convert the scrap back to high quality ingot. Automotive use has grown because of the low density of magnesium. This property is the one of the biggest problems to overcome in shipping scrap. Gates and runners from die casting are very irregular shapes and it is very hard to load a truck with enough material to get a low shipping cost per pound. Recent new equipment companies have developed magnesium equipment that is specifically designed to recycle, refine and cast secondary magnesium metal. These melt cells are supplied as integrated units to magnesium casting sites. The cost and effectiveness of this approach will be discussed.

Jan 1, 2000

By San-chuan Tang, Wen Chen, Shun-ming Ning, Kan-ping Yu, Qiang Zhao, Xue-yong Xing

"A new type of desilication agent (PA-2) was selected by experiment based on the analysis of the characters of silica gel, and the influence of desilication type, desilication dosage, pH value, temperature and aging time on the desilicating effect was studied. The test results showed that on the conditions that pH was 2.0, temperature was 20""C, aging time was12 hours and the dosage of desilication agent was 0.23%, the desilication rate was higher than 93% in solution.IntroductionVanadium is an important strategic resources, which applies to steel industry and petrochemical industry. The main materials for vanadium product are steelmaking vanadium slag, stone coal and containing vanadium waste catalyst, etc. And stone coal is a low-grade carbonaceous silicified vanadium resource, which is unique material for vanadium extraction in China. Meanwhile, our stone coal reserves is No.l throughout the world.The silica acid solution containing vanadium is produced by acid leaching of raw stone coal or its roasted ore. The silica content of this solution is mostly high, besides, when pH is higher than 2 , the solution is unstable. Furthermore, it is very easy to generate gel substance with the increasing of pH value and standing time. 'Ibis silica gel is composed of colloidal particles with the size in 0.001 - 0.1 um. As a result, it is very hard even impossible for the following operation of solution."

Jan 1, 2013

By D. L. Stewart

"Melt loss is usually one of the highest individual cost items in the operation of ah ingot casting facility. While melt loss and the resulting cost for the entire facility is usually well known (at least via standard cost accounting), dross generation and melt loss for individual unit operations within the plant are usually not known. Thus, the financial impact of various practices, alloys and scrap types is not known. Development of an accurate, relatively low-cost technique for measurement of melt loss at commercial scale would aid in understanding melt loss for existing units, as well as evaluation of the melt loss impact of alternate processes.This paper will describe a methodology developed at Alcoa for accurate and inexpensive measurement of melt loss at commercial scale. The methodology has been used to evaluate the impact of scrap type, melting practices, and dross treatment technology on melt loss."

Jan 1, 2000

By S. S. Chabot, S. E. James

A recent survey of major steel companies worldwide revealed the importance of recycling zinc units from electric arc furnace (EAF) dust, mill scale, blast furnace dust and other zinc containing streams within the steel industry. Many processes have been developed and installed in response to this challenge. The most successful approach involves the production of a crude zinc oxide and its sale to primary zinc producers to recover the metal values. The problem with this process is the high concentration of halides in the crude oxide. This type of material cannot be processed directly in an electrolytic zinc plant because of the corrosion problems it will cause in electrolysis. In 1999, Big River Zinc installed a zinc oxide receiving and washing plant to minimize the impact of halides in its electrolysis circuit. A description of the washing plant and the initial operating results are presented in this paper.

Jan 1, 2000

By C. M. Acuna

Scarcity of high grade copper low impurity content ores is a reality and processing of low grade dirty concentrates is a need. In spite of this fact, innovative strategies have to be looked at to comply with day to day more stringent environmental regulations. From this perspective the production of matte grades over 70% in copper presents several merits, but it must be contrasted with the fractional distribution of impurities reporting to the condensed phases. Converting of white metal high in arsenic content results in moderate fraction of arsenic to gas, but high deportment to blister. Therefore, production of anode copper, as required by the electrolytic refinery, may result in several operational difficulties. Furthermore, by recycling the flue dust and slag produced in the smelting-fire refining cycle, the arsenic content in the feed to smelting increases and so does in the resulting anode copper. The Teniente Converter, as a smelting unity, has probed suitable for production of high matte grade near white metal composition but regarding distribution behaviour of impurities there is lack of reliable data, specially when processing concentrates over 1% in arsenic content. In the new scenario, i.e. low grade copper high arsenic content concentrates, to fully asses the merits of this technology the effect of matte grade, secondary materials recycling and arsenic in feed upon the distribution coefficient of arsenic between slag and matte, mainly, must be evaluated both from a theoretical approach and by use of industrial data. Based on available data correlations of distribution coefficient, matte grade and matte/slag ratios with arsenic in feed and copper content in slag are worked out. Based on these results suggestions as to matte grades facilitating to deal more efficiently with the handling of smelting byproducts are proposed.

Jan 1, 2006

By Md Sazzadur Rahman

Electrochemical Impedance Spectroscopy studies were conducted on two organic thermal energy storage materials; Neopentylglycol (NPG) and 2-Amino-2-Methyl-1,3-Propanediol (AMPL). The ionic conductivities and dielectric relaxation times in the low temperature ordered a-phase (monoclinic for both NPG and AMPL) as well as high temperature orientationally disordered cubic y-phase are reported.

Jan 1, 2006

By Daniel E. Groteke

This paper describes a new technology which allows aluminum drosses to be processed at the generating melting furnace to recover available metallic values. The systems, offered in both manual and automatic modes, are capable of processing quantities ranging from 15 to 200 lb. per cycle, and recovering up to 90% of the aluminum with a combination of agitation and chemical reactions. In the automatic mode, the separation of molten alloy and de-metallized dross is achieved in less than five minutes process time. The recovered alloy, of largely unchanged composition, may then be returned while at elevated temperature to the original melting furnace to achieve an additional saving of energy.

Jan 1, 2000

By D. G. Schmidt

Tests were conducted on C86200 high-strength yellow brass in order to ascertain the effect of a low level of nickel on the mechanical properties on this alloy. A series of two alloys was studied, one of which had a nickel content of 0.85% and the other with <0.05% nickel. Copper and aluminum content ranged from 62.5% to 64% and 3.2% to 4.6%, respectively. When compared by zinc equivalents, a nickel addition of 0.75% in high-strength yellow brass does not act like copper but raises the tensile strength, 0.5% yield strength and BHN while lowering the elongation.

Jan 1, 1999

Sodium is added to aluminum-silicon eutectic alloys to modify the structure. The ideal amount is about 100 ppm but due to the fact that sodium is lighter than aluminum and can float to the surface where it bums, oxidizes ad volatilizes, a far greater amount is usually added. Furthermore, as the sodium is continually lost from the alloy the optimum amount is only present for a limited time. The net result is a process which is hard to control, produces fumes and a considerable amount of dross. It is shown that by electrochemically titrating sodium through a tube of sodium beta alumina electrolyte that the sodium can be added continuously in a controlled way. As the sodium is added to the bulk of the aluminum, there is no sodium on the surface of the alloy so that little surface oxidation occurs, and no fumes and dross are produced. This leads to an improved product and working conditions.

Jan 1, 1995

By K. H. Ho

This paper describes a simplified numerical model which is used to study the skull formation of liquid metal on a rapidly rotating disc in centrifugal atomisation. The skull formation is one of the problems limiting the wide use of centrifugal atomisation. The enlarging skull on the atomising disc reduces the yield of metal powder produced and produces a resistance to the centrifugal force which worsens the quality of the powder. It is costly and often difficult to study the flow behaviour by experiments due to the complex heat transfer and phase transformation during the processing. Computer modelling is therefore a powerful tool for mechanistic understanding of centrifugal atomisation. This paper investigates the flow pattern of the melt on the rotating disc as a function of initial temperature, melt flow rate and disc rotation speed as well as the physical properties of the melt, such as density, surface tension and viscosity using the commercial package Flow-3D. Keywords: Solidification, Rotating disk, Centrifugal Atomization

Jan 1, 2003

By K. Eto, H. Akiyama, T. Iwamoto

The Hikoshima smelter carried out an expansion project in 1997 and increased its production from 59,200 t/y to 71,000 t/y. The leaching process and the casting process had production capacities of 84,000 t/y, but because of the electric power situation in Japan, the production capacity in the electrolysis process was limited to 59,200 t/y to justify the production cost. Electrolysis was the bottle neck of the plant. In order to eliminate a part of this bottle neck, and considering the electric power situation in Japan, a way to increase the production during the time when the electric power rate is low was sought. In practice, we increased the number of cells by 36, and further improved the operation procedures in the cellhouse. For example, we improved the working efficiency of the cells, improved the productivity during the night time, decreased the unit power consumption and improved labor productivity. Accordingly, this paper describes the recent operations at the Hikoshima plant.

Jan 1, 2000

By William Ewing

Copper is rapidly being adopted by the semiconductor industry as the interconnect material of choice. The aqueous processing techniques used generate wastes such as spent electrolyte from electroplating, electroplating rinse water, copper solutions from removing copper from the back of the wafer and CMP waste streams. We are examining the use of chelating resins as a means of recovering copper from these streams within the processing plant, thereby allowing recycling of process water and minimizing hazardous waste disposal costs. We have examined the effect of model plating additives (and other organic complexing agents) on the efficacy of Dowex M4195. Although these might have had a significant effect, commonly used electroplating additives polyethylene glycol (PEG), benzotriazole (BTA), thiourea, glycine, and 3-mercapto-1-propanesulfonate (MPSA) each had little or no effect on the ability of the resin to chelate copper and remove it from solution. This suggests that Dowex M4195 could be useful for treating waste solutions of rather variable compositions.

Jan 1, 2003

By Ian M. Ritchie

Right across the universities of the developed world, the traditional disciplines of physics and chemistry are losing ground. Extractive metallurgy, which depends so heavily on chemistry, is also contracting despite a clear need for people with this kind of training in the mining industry. Reasons for this loss of popularity are discussed in this paper. High on the list is one of image. The extraction of metals is widely seen as a dirty, polluting, sunset industry which involves working in remote and uncomfortable corners of the earth for inadequate compensation. Ways in which the image problem can be overcome are considered. It is concluded that a concerted effort needs to be made by the universities and industry to redress this situation. The importance of extractive metallurgy, both now and in the future, when a greater emphasis will be placed on sustainability and recycling, needs to be stressed. In addition, courses need to incorporate training for a career path that leads on beyond extractive metallurgy.

Jan 1, 2003