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By D. J. Senor

Closed chamber incineration (CCI) is a novel technique by which irradiated nuclear graphite may be destroyed without the risk of radioactive cation release into the environment. The process utilizes an enclosed combustion chamber coupled with molten carbonate fuel cells (MCFCs). The transport of cations is intrinsically suppressed by the MCFCs, such that only the combustion gases are conducted through for release to the environment. An example CCI design was developed which had as its goal the destruction of graphite fuel elements from the Fort St. Vrain reactor (FSVR). By employing CCI, the volume of high level waste from the FSVR will be reduced by approximately 87 percent. Additionally, the incineration process will convert the Sic coating on the FSVR fuel particles to SiO2, thus creating a form potentially suitable for direct incorporation in a vitrification process stream. The design is compact, efficient, and makes use of currently available technology.

Jan 1, 1994

By Patricia Negrini Siqueira

Abstract. Polymers are susceptible to changes in their chemical structures that affect their mechanical properties under weather condition. Exposure of plastics to UV radiation causes a loss in their mechanical properties and/or change in appearance, including reduced ductility, color changes, yellowing and cracking. Today, there are several additive systems (light stabilizers) developed to work according to resin, final application, type of cultivation, and other characteristics. This study evaluates the different additive systems (Hindered Amine Light Stabilizer - HALS, nano calcium carbonate - NPCC, nZnO and nTiO2), applied 0.75% (in weight) in linear low density polyethylene (LLDPE). The samples were mixed by high rotation homogenizer and extrusion. Later, the samples were molded by injection and aged in QUV-B simulating 6 months of exposure to weather. Tests of FT-IR and tensile strength comparing to the non-aged samples were carried out in order to evaluate the performance of several additive systems.

Jan 1, 2015

By Cleusa Cristina Bueno Martha de Souza

Nowadays in Brazil the final disposal for spent batteries include sanitary and industrial landfill for hazardous waste from domestic waste and industrial waste respectively. The problems of environmental impact caused by spent batteries had been discussed of several years, considering the fact of metals contents, like Cd, Hg, Pb and Zn. Some techniques are been proposed for recycling this type of waste in order to protect the environment while bringing also economic advantages of recovering metals. The reclamation of metals from secondary raw materials had been employed and further applications of this flexible technology are planned to the future. The processing of metals solutions involving hydrometallurgical techniques is an efficient method for recovering metals, since it provides completely recovery of metals with low energy requirements. This paper discusses the spent alkalline batteries characterization and leaching stage experiments results with sulphuric acid as leachant. After batteries dismantling by mineral processing techniques, the black powder sample produced was submitted to diffraction X-ray characterization and atomic absorption spectrophotometry in order to verify all the substances presented. Some experiments were carried on to develop a hydrometallurgical process for initial metal recovery aiming to get Zn into a soluble form on aqueous solution in order to propose the next stages of purification and recovering Zn, as electroplated deposition. The sulphuric acid was chosen not only for being cheaper than other leachants but also for improving the extraction of soluble Zn as ZnS04 form at diluted acid concentration. Batch laboratory experiments leaching procedure were conducted to determine appropriate leaching conditions from the viewpoint of maximize zinc extraction. In these tests an amount of dry powder batteries was added to different acid concentrations and solid/liquid ratio and after leaching and filtration the aqueous solutions were submitted to atomic absorption spectrophotometry analysis to verify the Zn content.

Jan 1, 2000

By T. C. -M. Cheng

Iron removal and disposal in zinc plants has imposed a major environmental challenge to the industry. Among the existing options of precipitating iron as jarosite, goethite, and hematite, the Hematite Process seems to be the best candidate for the future development of a waste-free technology, because of its potential of producing saleable iron oxide residues for feed in iron-steel making industry. Unfortunately, under the current practice of the Hematite Process, it is not possible to produce iron residues clean enough to meet the specifications of the said industry. In this paper, the practice of industrial hematite precipitation and the relevant technical literature are reviewed with the objective to identify the critical processing parameters which are responsible for the contamination of hematite, particularly with sulfur and zinc. The analysis is conducted from a crystallization theory standpoint with emphasis given to the role of supersaturation with respect to the cleanliness of hematite precipitates.

Jan 1, 1997

By I. Gaballah

The electrochemical behavior of a chalcopyrite concentrate having a high pyrite content was studied in HC1 by potentiodynamic, potentiostatic and galvanostatic experiments using a cell having separate anodic and cathodic compartments. Anodic oxidation of chalcopyrite particles was realized both by their contact with the cunent feeder and by reaction with ferric and cupric ions. An increase of current leads to a more selective dissolution of chalcopyrite. Surface passivation was observed after an electrolysis time related to the cell current. Cathodic reduction of chalcopyrite concentrate seems to be more promising. Almost complete conversion of chalcopyrite to a copper sulfide (Cui.8.S) is observed, whereas no reaction of the pyrite was detected. This confirms the possible selective dissolution of copper from the chalcopyrite concentrate. Copper sulfide obtained by cathodic reduction was leached using a cupric chloride solution.

Jan 1, 1994

By Ma Lijuan, Zhang Yubing, Wang Bo, Sun Huilan

The effect of lime ratio on phase composition and alumina leaching property of MgO-contained calcium aluminate clinker were investigated by analytical reagent, the XRD analysis of its mechanism was discussed. The results showed that: when the sintering temperature was 1350 ℃, C/A was 1.4, A/S was 1.3 and the content of MgO was 4%, the increase of the C/A promoted the formation of C12A7 and restrained the formation of Q-phase. The alumina-leaching ratio of the clinker (A/S was 1.3) was increased from 74.33% to 91.34% when the content of CaO was 5.21%.

Jan 1, 2015

By Ki Bui Ma

Momentum wheels with superconducting bearings can integrate both attitude control and energy storage functions, with attendant savings in the total volume and weight of hardware, and power consumption, all of which are in short supply on mini-satellites. We have built and tested a prototype with a wheel of mass 1.9 kg, diameter 3.25 in, and height 3 in, which can store 3.5 J-sec of angular momentum and 5 kJ of energy when it rotates at an angular speed of 15000 RPM. The energy density of 2.5 kJ/kg achieved is comparable with the lower range for lead-acid batteries. To show that the wheel is energy efficient, we have performed spin down tests and measured the input power required to sustain rotational speed. Results indicate that power consumption, even accounting for the needs of cooling system, is significantly smaller than that for state of the art commercial reaction wheels.

Jan 1, 2002

By Sevinc Yildirim, Cigdem Oruclus

"Metal-Porous Silicon (PS) based structures dipped in water show the direct hydrogen fuel cell behavior. The effect of the thickness of the cupper (Cu) film on the electrical properties of direct hydrogen fuel cell is studied by fabricating Cu/Porous Silicon/n-Silicon/Indium structures. PS samples were produced electrochemical etching of n-type single crystalline silicon with a resistivity of 1,25 Ocm and (111) orientation. The thin films of Cu with different thickness between 200 and 600 nm were deposited on PS surface by electron-beam technique. Investigation of the effect of Cu layer on the performance of the structure indicates that the performance parameters such as open circuit voltage (Voc) and short circuit current (Isc) strongly depend on the Cu layer thickness. It was observed that the divice with an 350 nm Cu layer exhibits the highest open circuit voltage (0,5 V), short circuit current (0,01 mA) and power density (10 W.m-2).IntroductionHydrogen is the most attractive and ultimate candidate for a future fuel and an energy carrier. Hydrogen is recognized as the environmentally desirable clean fuel of the future since it can be used directly in different types of hydrogen fuel cells [1]. In the past years, the rise in portable electronics requires the development of miniature fuel cells compatible with standard silicon micro fabrication technology. Most silicon micro-fuel cells have used the polyperfluo-rosulfonic acid membranes (Nafion R) as a proton exchange membranes (PEM) that is not really integrated with standard micro fabrication techniques [2-5]. The composite materials such as inorganicorganic hybrid materials (Nafion-silica, Nafion-borosiloxane etc) are next generation of proton conducting membrane [4-8]. But, fuel cells run on pure hydrogen gas, which can be produced with other energy resources. Hydrogen smallest atom and thus the H2 gas can leak easiliy. The application of hydrogen for power sources has been greatly restrained due to the lack of safe and convenient generation and storage methods.A kind of hydrogen fuel cells Metal-PS-Si structures used as an energy water directly. There is no need pure hydrogen. Cu-PS-Si Schottky-type fuel cells with as proton-conducting membrane and the thin-film cupper catalist and water as fuel, which are interesting for fabrication of lowcost miniature fuel cells. Generation of the open-circuit voltage and short-circuit current has been observed by Cu-PS-Si structure dipping in different hydrogen-containing solution."

Jan 1, 2014

By W. Hoffelner

Plasma technology has become increasingly important for the treatment of several types of waste (toxic, nuclear, metal-bearing scrap). Plasma furnaces combine the advantages of a closed hearth process with a very versatile (several plasma gases can be employed) and effective heat source. It can be successfully used for recovery of metals with subsequent purification and/or vitrification of residuals from drosses or filter dusts.

Jan 1, 1994

By Catherine Cai

A granular sorbent, prepared by gel-coating polyethyleneimine (PEI) on high surface area silica followed by crosslinking with a low-molecular weight diepoxide, has significantly higher uranium capacity, greater salt tolerance, and faster kinetics than the commercial resin Dowex 21K. Though having lower U(VI)/Fe(III) selectivity than Dowex 21K, the gel-coated PEI affords much higher sorptions of both U(VI) and Fe(III) and also their separation by selective stripping with acid.

Jan 1, 1999

By James M. Lockwood

"Eureka Technology has developed and patented a technology for the recycling of EAFD. Through this process all constituents of the material become salable commodities or are returned to the steel making process. In transforming the EAFD ""waste"" stream into a ""process"" stream the Steelmaker eliminates potential liabilities and the uncertain future of current processes while further reinforcing its role as a recycler. This is a cost-effective and energy efficient technology that combines hydrometallurgic and electrolytic processes resulting in the recovery of salable metals. For instance, unlike pyrometallurgic processes, zinc is recovered in metallic form and no elements are volatilized. This on-site operation also eliminates expensive transportation costs. In summary this technology reduces the cost of dealing with EAFD by recycling material currently being landfilled.IntroductionWorld crude steel production reached a new record level in 2007 - 1.34 billion tons of which 31% was produced by EAF steel makers [1]. This resulted in the generation of over 6 million tons of EAFD. This steel byproduct contains significant amounts of lead, cadmium and other hazardous metals. In the United States the Environmental Protection Agency (EPA) has designated EAFD a hazardous waste (EPA waste code K061). With over 50% of steel production in the US coming from EAF steel making this byproduct represents the single largest source of solid hazardous waste generated."

Jan 1, 2008

By K. Adham

"Fluidized beds are utilized in a wide range of high-temperature applications throughout the metals and materials industry. Their main advantage is the fast and uniform heat and mass transfer between the hot combustion gases and the particulate solid feed. A further benefit can be the lowering of the processing plant's energy consumption, through heat recovery from the fluid bed processes used for solids heating. Here, the enhanced energy efficiency of fluidized systems is investigated and the modeling results are discussed for three configurations: the flash tube, the single bubbling bed and the multi-stage fluid bed. Key thermal design aspects of each system are identified based on results from process simulations, in order to benchmark their main operating features and overall energy efficiency. Suitability and applicability of each configuration is also discussed based on a number of process and material property considerations.IntroductionCombustion based heating of particulate solids is commonly done using three different types of fluidized beds. The flash tube (FT) is similar to a hot pneumatic transport system. The single-stage fluidized bed (FB) typically uses in-bed combustion. The multi-stage fluidized bed (MSFB) can have two or more stages stacked into a tower.Flash tube (FT) suspends the incoming solid charge in a high-velocity stream of hot combustion gases. To maintain the solids suspension in the FT, two parameters are required: high velocity for elutriation of the particles and adequate solid-to-gas ratio for avoiding high pressure drops and solids drop-out [l].The fluid bed (FB) works at much lower velocities than the flash tube. Therefore, most of the solids are not conveyed in the gas stream, but are only suspended in a liquid-like manner. At minimum fluidization velocity (Umr), the gas flow exerts just enough force on the solids to keep them suspended in place [2].Multi-stage fluid bed (MSFB) heats up the solids as they are transferred from an upper bed level to a lower one, counter-current to the rising flow of hot gases generated at the lowest stage. As the temperature and volumetric flow of the gases decrease from bottom to the top stage, smaller bed diameters can be used in the energy recovery stages [3]."

Jan 1, 2014

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 Norihiro Murayarna

Hydrothermal synthesis of K type zeolite was carried out by using coal fly ash as a raw material and KOH as an alkali source. The change in various physical properties of the obtained zeolite, such as the kind of zeolite crystal, cation exchange capacity, surface structure of zeolite and particle size distribution were investigated through the overall reaction of zeolitization. The reaction mechanism of K type zeolite from coal fly ash was investigated from these results in this study

Jan 1, 2002

By William Petruk

The primary requisite for a successful extractive metallurgy operation is to grind an ore fine enough to liberate the minerals so that they can be concentrated, or to expose mineral surfaces so that the minerals can be leached. The ease or difficulty of liberating or exposing the mineral grains is dependent upon the mineral textures such as grain size, crystallinity and bonding between mineral grains. In particular, mineral grains with straight grain boundaries and a weak bonding to other minerals are easily liberated and readily concentrated into high grade concentrates. In contrast mineral grains that have re-entrant boundaries and are strongly bonded to their neighbours are not easily liberated and will not produce high grade concentrates, even with regrinding. Similarly, inclusions that occur along fractures and grain boundaries can be readily exposed and leached. Whereas minute random inclusions in large grains will not be liberated or exposed unless they occur along planes of weakness.

Jan 1, 1995

By Dai Yongnian

The methods of treating zinc crust and its development in the last hundred years are compared and reviewed. There are better effects from normal pressure metallurgy turned into vacuum metallurgy. The traditional methods dezinc only. But we must consider that delead on further step. From lab tests to industrial scale experiment are researched. The first step-dezinc, second-delead, crude ,metal of, zinc, lead and silver are produced, The flowsheet of treating zinc crust are simplified, material consumption reduced, work condition improved, environment protect mended. This method is pointed out that its application can be expanded.

Jan 1, 1992

By A. V. Tarasov, V. M. Paretsky

"The knowledge of the true phase composition of the liquid slag is a very important problem, mastering of which grants the possibilities for the scientifically founded choosing of the decoppering method of the autogenous smelting slags. The investigation using different methods of the phase composition of the flash quenched autogenous copper melt's slags has shown, that the most effective method of the slags' decoppering during smelting with the white matte production is the flotation of the recrystallized slags. In this work the authors posed the problem to realize the slags quenching with the rates similar to those, which are used in the modem investigations devoted to the flash quenching of the ironcontaining alloys, with the subsequent study of the quenched samples using the Mossbauer spectroscopy methods in order to establish the connection between the liquid slag's structure and the metals losses with the slag."

Jan 1, 2000

By José Luiz Rodrigues Bravo

The production of electrolytic copper with assured quality corresponding to international standards, in a conventional electrorefkery of a custom smelter, is a hard and cautious task, if no advanced technologies for selective control of electrolyte impurities are available. The improper control of the amount of As , Sb and Bi in the anode that enter the tankhouse , attributable either to a bad schedule of concentrate input or to the unavailability of clean concentrates in the international market , as well as the lack of means to maintain the suitable level of these elements in the electrolyte together with other operational circumstances, can result in off-grade copper, as well as affect the starting sheet chemically and physically. This paper presents in a practical way the relationship between the operational conditions and the cathode and starting sheet quality produced at CMSA, covering the period of the last five years of operation, discusses the technologies available in the market for antimony and bismuth removal and compare the results of testwork, achieved in the laboratories of CMSA, using two resins not associated with patented technologies.

Jan 1, 1997

By M. Misra, J. Nanor

The precipitation and removal of arsenic from process waters can be accomplished with addition of lanthanum chloride alone or in conjunction with ferric sulfate. The long term stability of these corresponding precipitated compounds is critical from the disposal stand-point. In this paper the characterization of ferric, lanthanum and lanthanum-ferric arsenate compounds formed at room temperature in acidic and alkaline pH is presented. The characterization techniques used included zeta potential, XRD and SEM. Zeta potential measurements of ferric and lanthanum hydroxides in the presence of arsenate indicate that oxyanions of arsenate are chemically adsorbed onto the positively charged surfaces of these hydroxides. In alkaline pH there is desorption of arsenate species from the ferric hydroxide surface, hence the product is thought to be unstable. On the contrary, lanthanum arsenate is stable in alkaline pH. XRD patterns show that the ferric arsenate formed in acidic and alkaline pH is amorphous, whereas lanthanum arsenate and lanthanum-ferric arsenate formed in acidic and alkaline pH are crystalline.

Jan 1, 1999

By S. P. Mathew

The ISASMELT Lead Process is a continuous two stage process for the production of crude lead from concentrate. It is based on the use of a top entry submerged Sirosmelt lance to produce turbulent baths in which high intensity smelting or reduction reactions can occur. The process involves oxidizing the concentrates in the first stage to produce a high lead slag. This slag is tapped continuously and transferred down a launder to a second furnace where it is reduced with coal. Crude lead and discard slag are tapped continuously from this furnace through a single taphole and separated in a conventional forehearth. Process and engineering design work for a commercial scale Lead ISASKELT plant designed to produce 60000 tpa crude lead has been completed. This plant is planned to be operational in 1991.

Jan 1, 1990