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By R. F. Hammen

Heavy metal contamination of water is a problem of immense national and international proportions. However, effective cleanup is complicated both by the toxicity and the low concentrations of metals in wastewater streams. Using high performance chelation chromatography, the solid phase extraction and purification of extremely dilute metals from water was highly effective. The process is based on selective displacement of metals from a chromatographic column containing a chelating resin. The resin is characterized by extremely efficient adsorption kinetics which allow rapid and complete removal of the metals.

Jan 1, 1993

By Oscar Jaime Restrepo, Juan Camilo Restrepo, Jorge Ivan Tóbon

Portland cement is obtained by a conventional synthesis process from a mixture of limestone and clay at high temperature (1450 °C). This work reports the possibility to obtain cement silicates via alternative methods like Solution Combustion Synthesis (SCS), which optimize both time and temperature, and the consequences to energy efficiency and mitigation of CO2 emissions. The production of one ton of cement emits between 0.62 and 0.97 tons of CO2 into the atmosphere. In this process the CO2 emissions are between 21 and 59%. The combustion methods are chemical redox processes in which, at high temperature, a self-sustaining and fast wave is generated from using chemical precursors and organic fuels.

Jan 1, 2016

By Hector Carreon

During fretting, high points or asperities of the mating surfaces adhere to each other and small particles are pulled out, leaving minute, shallow pits and powdery debris. Sometimes these surface conditions are neglected, but they are important in some application such as the aerospace industry. In this research work, non-contacting and contacting thermoelectric power techniques are performed in fretted 7075-T6 and Ti-6Al-4V samples. It has been found that the contacting and non-contacting thermoelectric power measurements are associated directly with the subtle material variations such as work hardening and residual stresses due to plastic deformation produced in the fretting zone but surface topography. Therefore, both techniques could be used for a global characterization of the most relevant fretting induced effects. Potential of these techniques to monitor subsurface changes in other severe surface plastic deformation processes are clearly envisaged.

Jan 1, 2015

By Donald P. Ziegler, James F. Klausner, Srinivas S. Garimella

"By 2015, nearly half the world's population will live in ""water stressed"" areas. Production of fresh water utilizing waste heat from industrial processes has been identified globally as a research priority.About 15% of the electricity required to produce aluminum is lost as waste heat in the off-gas. However, the low temperature (low grade) of the heat limits reuse. The off-gases contain 50-150 ppm SO2 ; tightening regulations coupled with increasing coke sulfur levels are motivating SO2 control, for which seawater scrubbing is attractive for smelters with suitable access.We describe a process that produces fresh water, utilizing the waste heat while scrubbing SO2 . It uses direct contact between seawater and off-gas to humidify the off-gas. The vapor is subsequently condensed. In smelter trials, a unit treating a slip stream produced high quality water in the anticipated quantity, attaining over 95% SO2 scrubbing. Future work involves scaling the process to be economically attractive.BackgroundPopulation growth, coupled with industrialization and urbanization, are increasing demand for water. Water scarcity already affects every continent. Around 1.2 billion people, or almost one-fifth of the world's population, live in areas of water scarcity, and 500 million people are approaching this situation. By 2025, 1.8 billion people will be living in countries or regions with absolute water scarcity, and two-thirds of the world's population could be living under water stressed conditions (< 1,700 m3 per person annually) [1]. An assessment by the U.S. General Accounting Office revealed that under normal conditions, by 2013, water managers in 36 states in the USA anticipate water shortages, and that the number might grow to 46 states under drought conditions [2].The obvious choice to alleviate water scarcity is the 97% of available water in the oceans, which is saline and requires desalination for use in biological, agricultural and industrial applications. Technologies developed for desalination include Thermal Distillation, Reverse Osmosis (RO), Electro-Dialysis, and Vacuum Freezing. Distillation and RO are the most commercially prominent. Thermal distillation technologies include Multiple Effect Distillation (MED) and Multi-Stage Flashing (MSF). The report commissioned by the World Bank [3] is one of the many excellent references on desalination technologies. According to the International Desalination Association working paper [4], there were more than 17,348 industrial scale desalination plants installed or contracted by 2004. The total production from these plants is on the order of 8.3 billion imperial gallons per day. RO provides 47.2% of the total capacity. The leading thermal process, MSF, provides 36.5% of the total capacity. Although MSF and RO technologies currently provide the most cost effective means for desalination, their drawback is that they are very energy intensive, and whether or not they remain cost effective strongly depends on energy prices and energy supply."

Jan 1, 2012

By Thais Cristina da Costa Caldas, Carlos Mauricio Fontes Vieira, Alline Sardinha Cordeiro Morais, Sergio Neves Monteiro

"This work has as its objective to evaluate the effect of the incorporation of a glass powder waste obtained from discarded and Hg-cleaned fluorescent lamp into clayey ceramics used to fabricate bricks and roofing tiles. Formulations were prepared with incorporation of the waste in amounts up to 10 wt.% into the clayey body. Rectangular specimens were prepared by uniaxial mold-press at 20 MPa to fire at 850 and 1050°C. The physical and mechanical properties evaluated were: linear shrinkage, water absorption and flexural rupture strength. The microstructure of the fired ceramics was evaluated by optical microscopy. The results showed that the waste incorporation significantly improved the evaluated properties mainly at 1050°C.IntroductionFluorescent lamps use mercury as a main component for its operation. This metal is potentially toxic and can contaminate soils, animals and water bodies. The problem is aggravated if considerations are made with respect to the amount of lamps that are commercialized and discharged in emergent countries like Brazil [ 1].By using appropriate recycling processes applied to discharging fluorescent lamps it is possible to reuse most constituents of these lamps into new productive processes. A study has shown that one million common fluorescent lamps can generate 900,000 tubes of clean glass [2]. Moreover, this Hg-cleaned gloss may be recycled in different products.In fact, to recovery and recycle all materials that constitute the lamp instead of discharging them. This action protects the soil avoiding the formation of environmental passives [3]. It is also relevant to mention that the glass from fluorescent lamps is 100% recyclable while its permanence in the environment would correspond to very long time pollution, since its decomposition time is undetermined [4]."

Jan 1, 2011

By T. B. Braun

Cathode contamination is the principal factor affecting the quality of electrorefined copper. It is commonly accepted that annealability is unfavorably affected by the following elements, in decreasing order of adverse effect: tellurium, selenium, bismuth, antimony, and arsenic. Silver in cathodes has importance as it represents a nonrecoverable loss of silver to the refinery. Mechanisms for the contamination of cathodes by these elements are examined and the effect of operating variables on contamination, including anode composition, electrolyte composition, electrolyte temperature, addition agent practice, and electrolyte discard rate, are discussed.

Jan 1, 1976

By L. H. Gevantman

A program for the compilation of evaluated physical and chemical numerical properties data is being pursued at the National Bureau of Standards within the Office of Standard Reference Data. This program is being sponsored by the Department of Energy and managed by the Battelle Office of Nuclear Waste Isolation in Columbus, Ohio. The intent is to assemble a reliable body of numerical properties data concerning candidate mineralogical materials in which high-level radioactive wastes are to be buried. The ready accessibility of the data to site designers and the credibility achieved through the evaluative process are designed to help assess and compare the feasibility of each candidate material for use as a disposal site. Both generic and site-specific data are to be assembled. To date, generic rock salt properties have been assembled and published by the NBS as NBS Monograph 167. Details of the effort to produce this book are discussed.

Jan 1, 1982

By T. Plikas, L. H. Gunnewiek, L. Oshinowo

"Electric furnace smelting is one of the principal unit operations for ferroalloy production, and increased process intensity, improved availability, minimal maintenance and a longer campaign life are common objectives for electric furnace operation in order to obtain favourable economics of production. Furnace designers have continued to develop innovative solutions, e.g., furnace cooling systems, that have allowed these objectives to be realised and CFD modelling plays a key role in the design process. Enhanced understanding of the energy transfer process in the furnace and the ability to develop, evaluate and optimize components of the crucible design to match process requirements are the key motivators for modelling.This paper provides an overview of recent applications of CFD to the design of electric furnaces. The aim is to illustrate what can be done, and identify areas where further work is needed in this field. Examples include furnace bath simulation, crucible cooling system design, taphole design, baking of Soderberg electrodes, off-gas systems, and fume control and building ventilation. It is argued that the trend is for numerical models to become more encompassing while at the same time more accessible, and therefore further improvements in furnace design will be realised with continued and well validated modelling efforts.IntroductionOne of the main processing steps in ferroalloy production is the smelting of ore in electric furnaces. The three-electrode, AC submerged arc furnace is most prevalent method for smelting in the industry, with shielded-arc and DC plasma arc furnaces achieving limited application (1,2). Commercial furnaces range in size from a few megawatts to more than eighty megawatts of supplied power, and operate with the objective of maximising the return on capital invested. Maximising productivity and energy efficiency are two pathways to achieving this objective, through process intensification, increased availability, minimal maintenance, and increased campaign life for the furnace and associated equipment. Concurrently, the need to reduce the environmental impact of metal production by controlling the emission of particulate emissions, greenhouse gases, and other harmful by-products must also be met."

Jan 1, 2004

By Wenbo Luo, Kang Liu, Fusheng Mao, Jilai Xue, Jun Zhu, Chunlei Yang

Extracting alumina from coal fly ash (CFA) is of great interest for both environmental protection and recycling valuable alumina content. In this study, ultrasonic aided leaching process as an effective method was investigated to enhance extracting Al2O3 from CFA via concentrated sulfuric acid sintering. The influence of ultrasonic power and processing time were tested under the conditions as the same as those without ultrasound. It is found that the alumina extraction rate can reach 90.5 % with ultrasound assistance, while the ultrasonic treatment can reduce almost 15 ~ 30 min in leaching time and 5 ~ 10 oC in leaching temperature than those without ultrasonic operation at the same Al2O3 extraction rate. In addition, the ultrasonic can reduce calcium content by 6 ~ 8 % dissolved into the leaching liquid. SEM analysis also shows that the residue particle size with ultrasound is smaller than that without ultrasonic treatment.

Jan 1, 2015

By N. Kanarin

A thermodynamic study is reported on the chlorination of Fe(1-x.)O, Fe2O3, Cr2O3, MgO, Mg2SiO4 with chlorine in the presence or the absence of reducing atmospheres. The reactivities of these compounds as well as that of Mg3Si2O5(OH)4 using Cl2+N2, Cl2+air, and Cl2+CO gas mixtures were studied by non isothermal thermogravimetric analysis between 20 and 1000 °C. The same solids were chlorinated in a horizontal experimental set, during two hours between 350 and 1000 °C, in reducing and oxidizing atmospheres: The chlorination products were examined by XRD and SEM, and possible reaction paths were examined. Results indicate that the carbochlorination of these solids was better than their chlorination; Furthermore, the carbochlorination was performed at lower temperatures than those of the chlorination. Finally, the reaction extent was higher in the case of carbo-chlorination of these compounds. Based on these results, a process was suggested for the selective recovery of chromium compounds from the chromite concentrate.

Jan 1, 1995

This report presents overview of the authors&apos; results of thermodynamical investigation of some important metallurgical processes and phenomena. Among them: carbo thermal reduction of silica, and boron oxide, silicon carbide obtaining from different precursors, investigations on copper and manganese ores processing, investigations on pollution from different sources. Special attention is paid-to thermodynamical approach to investigation and estimation of multi component multi element compositions stability, developed by the authors. Also are discussed some auxiliary but&apos; important for the thermodynamical investigations issues.

Jan 1, 1997

By J. A. Brierley

A biooxidation-heap pretreatment process was field tested to evaluate enhancing gold recovery from a preg-robbing sulfidic carbonaceous ore. Newmont Gold Company&apos;s Gold Quarry sulfidic carbonaceous ore was inoculated with an iron-grown culture of Thiobacillus ferrooxidans to form a 495 ton test heap. Biooxidation was conducted for a period of 100 days. The most active period of biooxidation occurred during the first 40 days of pretreatment? About 35 to 40% of the sulfide was oxidized. The extent of biooxidation was considered good as the ore particle size was relatively large 58% >1?9 cm (&apos;/< inch). The larger particle size ore limited the extent of bacterial activity. The field test demonstrated the ability to conduct biooxidation in a small pilot test heap. Thiourea was evaluated for extraction of gold from the biooxidized preg-robbing ore.

Jan 1, 1995

By Wang Youlai

Sichuan province is the richest province for its waterpower resource in China, perfectly suited to develop a high consuming energy industry. Sichuan Aostar Group Company has two Aluminum smelters, Guangyuan Aostar smelter and Sichuan Aostar Smelter. The production capacity of Aostar Group was 240,000 tons in 2004. The construction scale of Sichuan Aostar Aluminum smelter is 250,000 tons per year. The first 168 GY-300KA pre-baked anode cells (125,000 tons/year) were put into production in 2003. This company has taken the lead in the use of the transfer gantry technology in China. Besides making the process of calibration the pot shell it has concentrated the efforts to construct cell lining elsewhere. This company also has taken the lead in China for using the EIRICH force mixing and cooling technology as well as in the world for the CP Company?s vertical ball mill technology that produces the pre-baked anodes. The carbon anode system completed its 190,000 tons/year production scale. This is the most advanced technology and the biggest scale pre-baking anode manufacture in China. Since the Sichuan Aostar 300KA cell was put into production, it runs normally and smoothly. Up to now the current efficiency is higher than 94% and the specific energy is only 13300kWh/T-Al.

Jan 1, 2006

By Grant Wallace, Rod James, Larry Twidwell, Ed Rosenberg, Courtney Young, Sean Dudley, Hsing-Hsin Huang, William Gleason, Jerome Downey

The use of applied chemistry in the production and optimization of leach solutions from Rare Earth Element (REE) ores and concentrates is being investigated. Ore and concentrate samples were characterized using scanning electron microscopy/mineral liberation analysis (SEM/MLA), X-ray diffraction (XRD), and Atomic emission inductively-coupled plasma spectroscopy (ICPAES). Multiple leach tests were performed to analyze the effects of temperature, residence time, and reagent concentration on the leaching of REEs. Analysis of leach solutions was carried out using ICP-AES. Modeling and statistical analysis of extraction behavior was carried out using DesignExpert 9. Modeling data for cerium extraction indicates that extraction is greatly influenced by temperature and reagent concentration, while leaching time plays a much less important role. Experimental design techniques are being utilized to optimize REE recovery. Results, conclusions, and directions for future studies will also be discussed.

Jan 1, 2015

By D. J. Brennan

A techno-economic study is in progress, examining process and product options for treating smelter gases containing various concentrations of sulphur dioxide. Key contenders have been examined within an Australian context using the following criteria: * Markets for products * Capital Costs * Operating Costs * Waste streams generated Product options considered thus far are sulphuric acid, sulphur, calcium sulphite and gypsum. The development of an appropriate overall framework for evaluating process and product options is discussed and findings thus far presented. The emerging techno-economic study offers promise as a constructive guide to future policy decisions by industry and government.

Jan 1, 1994

By Gregor Kücher

Lack of basic knowledge on the semi-direct recycling methods for hard metals hinders the application on an industrial scale. However, advantages like reduced expenses and lower environmental impact draw interest at future potentials. Consequently, this report aims to offer insight into the influence of varying bulky hard metal substrates during their lixiviation in acidic media with an oxidant. The statistical software Modde 11 assisted in the development of a design of experiments (DOE) for evaluation of the impact of average grain size, binder and tantalum carbide (TaC) content on the leaching characteristics. The other experimental parameters were constant. Among them were temperature, solution concentration and quantity, duration and substrate surface exposed to liquid volume. Eventually, prediction plots and factors of the computed model equation describe the effects of varying substrate qualities on leached binder metal and selectivity.

By Esher Hsu

On July 5, 1997, Environmental Protection Administration of Taiwan publicized the recycling regulation of waste home appliances that include four items, namely, television, refrigerator, washing machine, and air conditioner. It is believed that this regulation pioneers the law enforcement of waste home appliances in the world. The objective of this study is to provide helpful base for amending recycling rates of waste home appliances. This study investigates the collection and recycling costs of waste home appliances in accordance with these newly established routes and facilities, respectively. Cost survey was conducted among collectors and recycling plants of waste home appliances; consequently, the collection and recycling costs were analyzed, correspondingly. Results provide some suggestions regarding recycling route, recycling system, recycling rates paid by manufactures and importers, recycling subsidies to collectors and recyclers. Those suggestions may provide useful policy implications to EPA for the future decision-making regarding the recycling of waste home appliances.

Jan 1, 2003

By Yong Hack Lee

Nonferrous smelting processes have been through a rapid transformation since the beginning of 1980. The copper smelting technology has changed from the conventional Blast Furnace process to the Flash Smelting and MIB process. In the field of lead smelting, the technology has changed from the Blast Furnace Smelting to the Direct Smelting such as QSL and KIVCET. In 1992, Onsan Refinery successfully commissioned Direct Smelting QSL technology for lead. The QSL could produce more than 160,000 ton per year of lead bullion from lead concentrate and various residues. Moreover, since the year 2000, the TSL (Top Submerged Lance) Technology utilizing the same Direct Smelting process has been successfully commissioned to treat lead concentrate as well as lead sulfate residue produced from a hydrometallurgical zinc plant. This paper presents and compares the energy flows of lead smelting processes such as a conventional process and the Direct Smelting Processes plotted on the Pb-O-S phase diagram. The oxygen potential diagram suggests how to control the oxygen potential in the furnace. Also, it describes the recent operational experience in the TSL plant of Onsan Refinery with necessary mass balance of key elements.

Jan 1, 2003

By Ailton S. Ferreira, Rubén J. Sanchez Rodriguez, Sergio N. Monteiro, Felipe Perissé D. Lopes, Teresa E. Castillo

"Polyester composites reinforced with natural lignocellulosic fibers have, in recent times, been gaining attention in engineering areas as lighter and cheaper alternatives for traditional composites such as the ""fiberglass"". One of the strongest, the curaua fiber, is today being considered as reinforcement of composites for automobile interior parts. In fact, several research works are currently being dedicated to curaua fiber composites since physical and mechanical properties are required for practical uses. In this work, the thermal behavior of polyester composites reinforced with up to 30 % in volume of curaua fibers was investigated by differential scanning calorimetry, DSC. The results showed endothermic and exothermic events associated with water release and possible molecular chain amorphous transformation. Comparison with similar composites permitted to propose mechanism that explains this DSC thermal behavior.IntroductionThe modem composite materials, especially those reinforced with synthetic fibers such as glass and carbon, have been used since last century to attend the demands required by most technological fields, from home appliances to aerospace [1]. In fact, fiber composites offer significant advantages over monolitic materials, such as common metallic alloys, plastic and ceramics. One of the most important is the ratio between the ultimate stress and the density, known as the specific strength. For example, in common glass fiber polymer composites, the so called ""fiberglass'', the specific strength of around 400 MPa.cm3/g is higher than any conventional monolitic material. However, drawbacks exist. The energy required to fabricate ""fiberglass"" generates large emissions of C02, which are responsible for global warming. Moreover, ""fiberglass"" is not recyclable and cannot be incinerated [2]. As a result, most synthetic fiber composites end up in landfills or contribute to rivers and oceans pollution."

Jan 1, 2011

By William E. Frazier

The presence of minute amounts of sulfur (10ppm) in nickel-base superalloys has been associated with reduced oxidation resistance and the premature spallation of protective coatings. Removal of sulfur by annealing these alloys in a hydrogen atmosphere has been successfully attempted by several researchers. This paper examines the fundamental thermodynamics and kinetics governing hydrogen desulfurization of elemental nickel. Limiting conditions for successful desulfurization are delineated. Assuming that the diffusion of sulfur is the rate limiting process of desulfurization, the effectiveness as well as time associated with hydrogen desulfurization is explored.

Jan 1, 1994