Search Documents

By Yanjie Liang

Elemental sulfur and volatilization kiln slag(VKS)containing heavy-metal produced by smelter factories were used to produce sulfured building material. The effects of heating mode, material proportion (MSulfur:MVKS), size of waste particles and ratio of aggregate to filler(A/F) on the mechanical properties and leaching toxicities of solidified stuff were investigated. The optimal conditions for the solidification are stepped heating mode, 3:7 ratio of MSulfur to MVKS, particle size less than 150µm and 3/17 ratio of A/F. Under the above optimal conditions, the compressive strength of solidified stuff rises to 35 MPa, and water absorption is down to 4%-6%.Furthermore, when NaOH is applied as an additive in the process of solidification, the 2+concentrations of most heavy metals except Pb have reached the national leaching toxicity standard. The results of X-ray diffraction reveal that sulfured solidification is caused by the physical encapsulation rather than chemical transformation.

Jan 1, 2010

By Hans Korfmacher

Product take-back regulations implemented in Europe have presented significant challenges to the consumer electronic product and battery industries. Initially companies established single compliance organizations within individual Member States. These programs met business needs but were inefficient and costly. They were protected from pressures of marketplace competition and could not leverage economies of scale. In order to address these problems P&G, Hewlett Packard, Sony and Electrolux conceived a pan-European compliance organization to collect waste electronic equipment Europe-wide. This organization, called the European Recycling Platform (ERP), operates in competition with existing national compliance systems. Since 2005 ERP has collected 800,000+ tons of waste electronic products and delivered millions of dollars in cost savings. This presentation reviews the steps needed to establish successful competitive collection organizations that provide sustainable recycling at the lowest cost.

Jan 1, 2010

By Jilai Xue

Oxygen gas bubbles generate on anode during Pb electro-deposition process in PbSiF6-H2SiF6 aqueous solutions at room temperature. Cell voltage varies as the bubbles formed on the anodes surface. The bubble layer on the anode makes a voltage drop that consumes energy in the Pb process, which can be reduced by applying ultrasound on the anode. The effects of ultrasound frequency and anodic current density were investigated with ultrasound on and off, alternatively during the Pb electrode-position process. The removing of the gas bubbles were recorded in association with a drop in the cell voltage. The cell voltage can be lowered by 4% - 6% with ultrasound, which has potential for energy saving in Pb production.

Jan 1, 2010

By Mark Tjerkstra

In ,1993, the WMC Resources Ltd.-owned Kalgoorlie Nickel Smelter, underwent a capacity upgrade. This capacity increase was offset by .air quality control restrictions limiting the smelter's availability to 80%. As the direct. result of this limitation, WMC Resources Ltd commissioned a double absorption contact ,acid ,plant for the desulphurisation of furnace waste gas in August 1996. The history and the impact of the acid plant on S02 emissions and air quality is reviewed. General descriptions of the other aspects of the Kalgoorlie Nickel Smelter's Environmental Project are also included in the paper. Information on 'the design features? and operating practices that relate to or contrast with practices at operations visited by KNS personnel prior to acid plant commissioning provide the paper's focus. Smelter operation has changed markedly from unstable operation prior to 1997 to continuous" operation with little down time due to mechanical or process failures resulting in increased smelter availability to more than 90%

Jan 1, 1998

By V. Kamavaram

Keywords: Recycling, Aluminum Metal Matrix Composite, Ionic Liquids, BMIC Recycling of aluminum metal matrix composites (MMC) via electrolysis in ionic liquids at near room temperature was investigated. The electrolytic melt comprised of 1-butyl-3-methylimidazolium chloride (BMIC) and anhydrous AlCl3. Impure aluminum composite (Duralcan MMC Al-380, 20 vol % SiC) was electrochemically dissolved at the anode and pure aluminum (>98%) was deposited on a copper cathode. The deposits were characterized by scanning electron microscope, X-ray diffractrometer, and mass spectrometer. The influence of various process parameters such as concentration of electrolyte, and applied cell voltage on the recycling process was studied. The recycling process yielded current densities in the range of 200-500 A/m2, and cathode current efficiency of about 85%. The results indicated that impurities such as Cu, Si, Ni, Fe, Mg, Mn, and SiC particles were removed as anode residue. Energy consumption of about 3.7-6.3 kWh/kg-Al was obtained at a cell voltage of 1.0-2.0 V and cell temperature of 100 ± 5°C. Low energy consumption and no emission of pollutants are the two main advantages of this process compared to present recycling processes.

Jan 1, 2005

By Jorge A. S. Tenorio, Chuanwei Zhuo, Joner O. Alves, Yiannis A. Levendis

"Reduction of combustion-emitted greenhouse gases, which are associated with global warming, may be achieved by use of CO2-neutral alternative fuels, such as bio-ethanol. Distillers Dried Grains with Solubles (DDGS) are the main co-products of the com-grain-based ethanol industries. In 2009, the North American production of ethanol from com was about 38 billion liters, which generated approximately 31.5 million tons of DDGS. Samples of DDGS were pyrolysed at temperatures of 600-1000 °C in a two-stage laminar-flow horizontal furnace, and a catalyst system was used to synthesize nanomaterials. This work presents a microstructural characterization of these nanomaterials by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that the nanomaterials produced from pyrolysis of DDGS were in the form of long, entangled, rope-like structures with rugged walls, lengths in the tens of microns, and axially non-uniform diameters in the range of 100-300 nm.IntroductionThe interest in ethanol has increased considerably worldwide due to the necessity of finding renewable and cleaner energy resources [1, 2]. According to the Renewable Fuels Association (RF A), the world ethanol production in 2008 was approximately 65.7 billion liters (17.3 billion gallons), which figure represented a 24% increase in the production over that in the previous year [3]. The major producers of ethanol are the USA and Brazil, which together account for 90% of world production. The main feedstock for ethanol in USA is com grain, whereas sugarcane predominates in Brazil [2-4]."

Jan 1, 2011

By Georges J. Kipouros

Anhydrous neodymium trichlorids (NdCl3), containing ~1 weight percent neodymium oxychloride (NdOCI) was prepared by the dehydration of neodymium trichioride hexahydrate (NdC13.6H2O). Dehydration of the hexahydrate was conducted in three steps. First, the hexahydrate was slowly heated in air to about 250 °C until all the low temperature water of crystallization was removed. In the second stop, the neodymium hydroxychloride (Nd(OH)2C1) fanned in the first step was decomposed by heating under argon to 430 ° C. Finally the salt was ground and then treated with HCl gas at 330 °C until practically all of the NdOCl was converted to NdCl3.

Jan 1, 1992

By Preston C. Holloway

Transformational roasting involves the heating of a material along with specific additives to induce mineralogical changes in the starting material. By controlling the chemical composition, roasting atmosphere, temperature and time of reaction, the mineral transformations induced during roasting can be engineered to control the distribution of valuable, or harmful, metals and to produce new mineral assemblages that are more amenable to conventional methods of metals recovery or to environmentally safe disposal. To date, this type of process has only been applied to the recovery of a limited number of metals, but current research is looking to expand the application of these techniques to the recovery of metals from a wider range of materials. An introduction to these techniques is presented along with preliminary results from their application to metals recovery from zinc bearing wastes, such as zinc ferrite leach residues and carbon steel electric arc furnace dust.

Jan 1, 2006

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 Sergio N. Monteiro

Natural lignocellulosic fibers are successfully replacing synthetic fibers in many engineering applications. In addition to well-known conventional lignocellulosic fibers, others with promising properties are now being considered. The present work investigated the mechanical and structural characteristics of a relatively high strength fiber, curaua (Ananas erectifolius) from the Amazon region of Brazil. The results obtained from tensile tests confirmed the superior strength while scanning electron microscopy (SEM) analysis displayed features that justify the possibility of using the curaua fiber as an effective reinforcement for polymeric composites.

Jan 1, 2006

By A. M. Ramalho

In the synthesis and sintering processes to obtain superhard materials, such as diamond and cubic boron nitride, deformable ceramic capsule is used as gasket to transmit and support the required high pressures and high temperatures, HPHT. The ceramics materials for these capsules should have special physics and chemical characteristics such as refractoriness, shear strength and compressibility. In this work, Bridgman?s anvil made of hard metal or speed steel was used to characterize some ceramics materials in terms of their maximum compressible thickness. Tests were also performed with different resin polymers used as binding mixture with ceramics powder. Chemical analyses and investigations through scanning electronic microscopic (SEM), X-ray and real tests for the synthesis of diamond were also performed. The results showed that local Brazilian calcite can be successfully used in the manufacture of HPHT gaskets.

Jan 1, 2006

By Adriana Gómez

White dross is a result of the aluminum oxidation during its primary production and is mainly composed of metallic aluminum, Al2O3, with minor amounts of AlN and some other oxides. Because of the great variety of phases, the quantitative characterization is complicated. This work shows a quantitative method to determine the main phases of white aluminum drosses by means of X-ray diffraction (the Rietveld method). Nowadays the Rietveld method is maybe the most useful method for obtaining quantitative phases information in multicomponent mixtures, this method permits relatively quick quantitative phase analysis by fitting the calculated X-ray diffraction profile with the observed one. The analysis were done using powder with a grain size less than 45 µm; to obtain the suitable material size the aluminum dross was grounded by ten minutes, several times. The grounded material was screened, and the material smaller than 45 µm was taken to quantitative XRD analysis. Keywords: Rietveld Method, Characterization, Aluminum dross.

Jan 1, 2005

By Ji-He Wei

Keywords: stainless steel, AOD refining, side and top combined blowing, mixing characteristics, water modeling The fluid mixing characteristics in the bath during the side and top combined blowing AOD (argon-oxygen decarburization) refining process of stainless steel have preliminarily been studied on a water model unit of a 120 t AOD converter. The geometric similarity ratio between the model and its prototype (including the side tuyeres and the top lances) was 1:4. On the basis of the theoretical calculations for the parameters of the gas streams in the side tuyeres and the top lances, the gas blowing rates used for the model have more reasonably been determined. The influence of the tuyere number and position arrangement, and the gas flow rates for side and top blowing on the characteristics has been examined. The results demonstrated that the liquid in the bath underwent vigorous circulatory motion during gas blowing, without obvious dead zone in the bath, resulting in a well mixing effectiveness. The gas flow rate of the main tuyere had a governing role on the characteristics, a suitable increase in the gas flow rate of the subtuyere could improve mixing efficiency, and the gas jet from top lance could make the mixing time prolong. Corresponding to the oxygen top blowing rate specified by the technology, a roughly equivalent and good mixing effectiveness could be reached by using six side tuyeres with an angle of 27° between each tuyere, and five side tuyeres with an angular separation of 22.5° or 27° between each tuyere. The relationships of the mixing time with the gas blowing rates of main-tuyeres and sub-tuyeres and top lance, the angle between each tuyere, and the tuyere number have been obtained.

Jan 1, 2005

02, NaCI03, H202, Na0CI and Ce+4 have been examined as oxidants in an alkaline carbonate system for uranium in in situ leaching. The South Texas and New Mexico ores contained up to 2.6 meqJg of reducing compounds which consume oxidants in the leading operation. Leaching rates did not increase linearly with the oxidation potential of the oxidants. A mild oxidant can be used to maximize uranium oxidation selectively and oxidant efficiency. 02 can oxidize most of the uranium mineral with an adequate rate and high oxidant efficiency.

Jan 1, 1990

By Emma Arakelova

?2?2 (98 %) vapour passed through a reactor at 25Pa where a Zn? target was placed at 273K- 373?. Experiments were carried out on a flow- type vacuum device. ?2?2 decomposition on Zn? surface accompanied by formation of a Zn-containing volatile complex which transferred to the gas phase, and Zn? deposited on a substrate at condensation. As the substrate, five sequentially located quartz cylinders were used at 293K- 423 K (?n). Decomposition of the Zn-containing complex on quartz substrates carried out as a first- order reaction. ?The complex decomposition constant (??) increased with the substrate temperature (?n=293 K, ??=7.05 sec-1;?n = 373 K, ?? = 87 sec-1;?n = 423 K, ?? =158 sec-1). ?The complex decomposition constant did not practically vary when the target temperature increased; the complex formation rate increased slightly.

Jan 1, 2006

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 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 Chang Chia -Fu

The generic structure of our bimesogens is shown in and for a typical blue-phase mixture of the type we describe here. We use mixtures of the ratio 33.4% (n =2.6), 34.1% (n =6.57), 36.6% (n= 11.15) with of the high twisted power (HTP) agent BD H1381(available from Merck Chemicals and described in ref. We then studied the electric-field dependency of the selective reflection in BP I* at 20.7 °C by applying increasing and the decreasing pulsed alternating current (a.c.) electric fields (100 Hz).

Jan 1, 2006

By Jilai Xue

Experiments with various industrial cathodes ranging from 35 wt.% to 100 wt.% graphitic and fully graphitized carbons were carried out in a laboratory aluminum electrolysis cell. Sodium and cryolite bath penetration into the cathode samples was measured by XRD and SEM-EDS analysis. For a higher cryolite ratio in the bath, the cathodes with lower graphitic carbons exhibited more sodium penetration than the fully graphitized. The increased graphitization in the cathode materials can reduce Na, NaF and Na3AlF6 penetration. SEM-EDS inspection reveals that the sodium and fluorides penetration within the cathode samples has different patterns for varying graphitization of the carbon materials. XRD quantitative analysis indicates that there is a large percentage of Na3AlF6 in the penetrated bath. The results can provide useful information for quality evaluation of the industrial cathode products.

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