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By Abhishek Asthana

The incineration of Municipal Solid Wastes (MSW) is an attractive process for reducing the volume of the wastes and recovering their energetic value, which, however, requires to be strictly controlled in order to limit its impact on the environment. In this context, we have undertaken the mathematical modeling of the different sections of a typical incineration plant. The combustion of the waste bed, usually carried out on a moving grate, is at the core of the process. This paper presents the 2-dimensional, steady-state model that we have developed for simulating the MSW combustion. The model describes gas flow through the porous waste particle bed, the gas-solid reactions, conductive and radiative heat transfers, drying of the feed, its pyrolysis and the emission of volatile species, combustion of the pyrolysis gases, the formation of char and its gasification by water vapor and carbon dioxide, and the consequent reduction of the bed volume. Pyrolysis kinetics distinguish between cellulosic and non-cellulosic materials and are experimentally derived from our laboratory measurements. The calculated results give a deep insight into the various involved phenomena, an example being the complete consumption of oxygen in a large zone of the bed and the related appearance of a char gasification zone. The influence of various operating parameters, like the temperature and flow rate of primary air, is presented and explained. Finally, the effect of stirring the waste bed on the moving grate is also analyzed.

Jan 1, 2006

By Olga K. Karakasi, Angeliki Moutsatsou, Ioanna Kavallari

"The present study focuses on the amelioration of the behaviour of high calcium fly ash (HCFA), investigating its application in a new environmental field: oil spill clean up. High calcium fly ash is a by-product of electric power plants, produced annually in large quantities, whose greater amount is landfilled. Some of its properties, such as its chemical and mineralogical composition, its fine particle size, its porosity, floating ability and hydrophobic character make it an attractive material for this purpose. Researches showed that when added to an oil spill, it forms a semi-solid phase, which allows the quite total removal of the oil, but it is not stably retained on the surface. In order to ameliorate its floating ability, the decrease in its specific gravity by mixing with a lighter material is investigated. In the present study the mixing with two materials, already used in oil spill clean up, sawdust and a polymer, has been examined. Addition of 15-25% w/w sawdust to HCFA results in a material with better performance than HCFA or sawdust alone: it has a satisfactory floating ability and allows total removal of oil. Addition of the polymer, however, has resulted in no significant amelioration of the oil sorption behaviour of HCFA, probably because no affinity between HCFA and polymer has been achieved.IntroductionCoal fly ash is a by-product of coal combustion in electric power plants, produced worldwide in huge quantities, approximately 500 million tones annually. High calcium fly ash (HCFA) is classified to class C presenting a (Al2O3 + SiO2 + Fe2O3) > 50%. The production of lignite fly ash in Greece comes up to 13 million tones annually, of which only 12% is used in construction applications, the other being landfilled [5, 6].Besides its limited application worldwide as a construction material, research is focusing on the development of new environmental applications, such as waste stabilisation and solidification, soil and water environmental improvement [9, 12]. For the application of fly ash in further environmental fields several chemical modifications have been applied, in order to improve its properties. Extensive research has been focused on the conversion of both coal and lignite fly ash to zeolite and its further application in environmental field, such as the uptake of inorganic (heavy metals and ammonium [8, 11]) or even organic compounds (methylene blue [15]) from waste water streams, or the use as molecular sieves, to adsorb water molecules, SO2 and NH3 from gas streams, due to the high cation exchange capacity and porosity of the produced zeolithic material. Furthermore, lignite fly ash has been combined with sodium silicate solution, prepared by treatment of rice husk ash, and tetrapropylammonium bromide, to synthesise hydrophobic zeolite ZSM-5 [4]."

Jan 1, 2008

By Carole Read

Hydrogen is under consideration by several countries for its potential as an energy carrier for transportation applications. In order to compete with vehicles in use today, hydrogen-powered vehicles will require a driving range of greater than 300-miles in order to meet customer needs and expectations. For the overall vehicular light-duty fleet, this dictates that a range of 5 to 13 kg of hydrogen be stored on-board (assuming a fuel cell power plant) within stringent system weight, volume, and cost constraints. Vehicular hydrogen storage thus constitutes a major scientific and technological challenge. To meet this challenge, the U.S. Department of Energy (DOE) initiated a ?National Hydrogen Storage Project? with roughly 40 universities, 15 companies and 10 federal laboratories, actively engaged in hydrogen storage research. Centers of Excellence in metal hydrides, chemical hydrides, and carbon-based materials have been established, as well as independent university and industry projects in the areas of new concepts/materials, hydrogen storage testing, and storage system analysis. Recent technical progress in each of these areas is discussed, as well as collaborative hydrogen storage activities under the recently established International Partnership for the Hydrogen Economy (IPHE).

Jan 1, 2006

By Alexander V. Derevyanko, Victor P. Popov, Alexander I. Raitchenko

"If an electric current flows along some electroconductive suspension in columnar form the solid particles are 'experienced thermal, mechanical, and electromagnetic influences.The objects were suspension Sn (liquid) - Ni-Cr-Mo-W alloy (solid particles). This is refractory alloy on the Ni base. The direct constant current (with density -106 A/m2 ) flowed through the named suspension during 180+300 sec. At the beginning of experiments samples were ones containing particles suspended uniformly in volume. Although density of solid particles was ~9x103 kg/m3 , i. e. higher than density of liquid Sn (-6.8x103 kg/m3 ), after end of this processing, the non-uniform distribution of particles in volume of samples was observed: concentration of Ni-alloy particles in lower part was smaller than their concentration in upper part of samples, and simultaneously their concentration is increased near outer surface. There was probably the natural convection of Benard-Rayleigh type which had carried, so lid particles upwards, and, in same time, there was the action of spatial Lorentz-forces directed to center forcing the radial movement.The knowledge of named phenomena can be useful for elaboration of technology of gradient dispersed materials and development of some materials science fields.IntroductionThe liquid metal with the electric current or under the alternating magnetic field is experienced compression. This action causes the pressure within metal and the change of the surface of the metal column (see, for example, [1-4]). One of results of such an electromagnetic compression is extraction of the foreign solid particles from a cylindrical liquid sample to surface in the radial directions. However, more complicated paths of the inclusions are observed under some conditions of electric treatment."

Jan 1, 1999

By Jorge Alberto Soares Tenório

Electronic components have precious metals like Au and Ag. These metals have a high performance in electric conductance. The recycling of the scrap, however is too difficult because of the presence of other metals like Fe, Al, Zn, Sn, ceramics and plastics, all together in electronic components. The aim of the present work was to define one way for physical separation to have metallic non-ferrous concentrates. It was used three kinds of scrap. I was used conventional equipment for mineral processing like hammer mill; screens, electrostatic and magnetic separation.

Jan 1, 1997

Off-gas cleaning from metallurgical plants requires? in many cases very low dust contents which are difficult to achieve with conventional scrubbers, even with high energy input. Lur.gi has developed a scrubber which improves the separation of the fine dust by electrical charge prior to. the scrubbing zone. An Electrostatic Scrubber has been successfully installed for the off-gas cleaning from slag' granulation after a waelzkiln achieving less than 1 mg/m3 in the clean gas.

Jan 1, 1992

By N. E. Ablesimov

Electron probe X-ray microanalyser of a coating deposited with "Elitron¬22A" electrospark alloying (ESA) set (anode - Cr, base-catode - chrome vanadium steel) has shown that the zone of phase forming can be divided into three parts: the coating itself, diffusion zone and a thermal affection zone in the base material. Waves of iron and chrome concentrations have been found in the diffusion zone. The authors interprete them as a phenomenon of substance self-organizing in the 30 pill deep diffusion zone, characterized by a change of compositions during the transfer of material from the coating to the base: coating - 20 µm (FeCr2), diffusion zone - 30 µm (Fe3Cr, FeCr, Fe4Cr, Fe2Cr), base - steel (Fe - 87 %, Cr - 12 %, V - I %). This ESA phenomen has been noted for the first time. It may be relative to the phenomenon of periodic formation of secondary products during the mutual diffusion of reacting substances in the case of a one-way reaction. Similar regular structures may appear in the diffusion zone during ESA of vanadium steels with vanadium, manganese steels with manganese and so on.

Jan 1, 1999

By Kenji Monden

A simple technique is presented to evaluate optical property of biomimetic microlens array (BMA) as an antireflective surface on a polydimethylsiloxane (PDMS) sheet. The integration of these structures is done by a thermoforming process. We have only UV-VIS spectrophotometer for optical evaluation apparatus. The transmittance of the sheet is measured with angled sample holder. The 50 deg. transmittance of 270nm pitch BMA on PDMS sheet increases from 87 to 92% after the moth-eye structure is introduced. The transmittance of 350nm pitch BMA on PDMS sheet increases from 87 to 96% after the moth-eye structure is introduced. The transmittance increases with increasing pitch of BMA. The results obtained using UV-VIS spectrophotometer with handmade sample holder.

Jan 1, 2015

By Andreas Dietrich

Laser off-gas measurement of CO, O2 and temperature has been carried online in EAFs. A visualization screen shows the values of CO and Oxygen and temperature for the entire heat, and includes the status of furnace equipment. The historical data of the heats are stored such that the furnace performance can be evaluated and optimized. A short comparison between laser based and conventional systems has been carried out related to speed, influence of dust, water, pressure, protection for bag house explosions. A high water and/or dust content in the sample does not represent a problem for this type of system. The measurement method works without interruption even under worst conditions such as dirty scrap, carbon injection etc. The installation was developed in conjunction with Marienhuette, Graz. They are 100% scrap based with a tap to tap time of ca. 46 min. Keywords: Laser Measurement, Off Gas, CO, O2, Temperature

Jan 1, 2003

By Yoshimasa Oda

The tank house of Tamano Smelter has adopted a high current density electrolysis operation applying PRC (Periodic Reverse Current) method and before 1991, it had materialized both high production capacity of 161,000 tons/year and high labor productivity. However, recent rapid rise of Japanese currency in foreign exchange market has urged us to further exert our efforts in reduction of labor cost. In order to achieve this goal of labor cost reduction, we have completed, in 1994, our phase four production expansion project which incorporated significant re-structuring of the organization and we have accomplished annual production of 191,000 tons/year. This project can be outlined as increase of number of cells for electrode exchange per day in the commercial electrolysis process to meet the increased number of cells and increase of the capacity of impurity treatment process. These improvements were done with minimum installation of new equipment and facilities and with achievements in efficiency and manpower saving of the existing facilities. Together with these improvements, rationalization in the starting sheet section was carried out by changing the material of mother blanks as well as changing their maintenance procedures. At the same time, the crane in this section was modified to enable automatic operation by a fuzzy control. As a result, we were able to save manpower equivalent to 5 operators in this section. With these improvements, the production capacity was increased by 18% and labor productivity by 25%.

Jan 1, 1996

By Huaming Yang

Infrared materials are a special kind of material widely used in military, biological engineering and chemical industry. However, the problems associated with them such as unstable properties, high cost and a high thermal expansion coefficient seriously restrict the development and the wide application of the traditional infrared materials with the SiC or ZrSiO4 matrix. The ultrafine quartz powder is normally used to prepare the infrared materials by hot-pressing technology. The aim of the paper is to investigate the thermal expansivity, the effect of the SiO2 size and the addition of AI2O) or Fe2O3 on the infrared emissivity of the quartz matrix of the infrared material (QMIM) in a 8-25um wavelength range. The results indicate that 89% of infrared emissivity and 0.4x 10.5°C of thermal expansion coefficient of QMIM can be obtained. The affeeting mechanism of Al2O) and Fe2O3 on the infrared emissivity of QMIM were also discussed.

Jan 1, 2003

By A. N. Aposhian

The electronics industry generates tin/lead bearing by-products that can be recycled for their metal value. This paper will cover the processes used to recycle these tin/lead bearing byproducts from the plating, circuit-board fabrication and assembly industries. Though these processes are well known to the companies who do the recycling, few outside the industry including the generators of the by-products, understand the processes or needs of the industry. This paper will give a broad overview of these processes, and describe the services provided by this industry. The paper will also touch upon the future of the recycling industry, including the legislative and environmental push for the elimination of lead from electronics.

Jan 1, 2000

By Mokka N. Rao

In this experimental investigation, the principal operating parameters of the spirals HC 1870 and HG 8/7 are determined for the hydrogravimetric separation of the friable siliceous iron minerals of the Piar Distric, Venezuela. Mineralogical characterization including optical microscopy of feeding materials and the products after separation are presented. Comparative analysis is made of effectiveness of productivity between the two spirals.

Jan 1, 1999

By Yeliz Demiraya, Onuralp Yucelb

"Production of strontium metal from its oxide was studied under the pressure of 1-5 mbar by methalothermic process. SrO with 99 % purity was used in the experiments. Effects of Al powder addition (100, 200, 300 % of stoichiometric ratio) and time were investigated on recovering of metallic strontium. Effects of BaO addition (100 %, 200 %, 300 %) was also investigated. The final residues were examined for their chemical composition. XRD, AAS and Flame Photometer were used for chemical analysis. More than 96 % of strontium metal recovery can be obtained.IntroductionStrontium is an element which is used in many advanced technology applications. Barium strontium titanat, strontium bismuth titanat, and strontium bismuth tantalat thin films are promising materials in ferroelectric and Schottky-based microelectronics technologies, especially for memory applications. Physical vapor deposition (PVD) techniques as magnetron sputtering, thermal evaporation and molecular beam epitaxy (MBE) are the most widely used methods for growth of these thin films [1-3]. In these techniques high-purity of Sr metal is used as evaporation sources and sputtering targets. Furthermore, metallic strontium is used as a ""getter"" in electron tubes, and as an alloying elements in aluminum alloys [4].The most used Sr compound is SrCO3 and widespread process used in production of SrCO3 is the hydrometallurgical carbonation of celestite. Although there are considerable amount of Selestite reserves, SrCO3 and strontinum metal are not being produced in Turkey, yet [5].Concentrated celestite (SrSO4) is conversed to SrCO3 in carbonate media. Black ash and direct conversion processes are currently used methods. There are many satisfactory studies about hydrometallurgical carbonation of celestite and decomposition of SrCO3 [6, 7]. Since strontium metal is produced from it’s oxide (SrO), SrCO3 needs to be decomposed to SrO."

Jan 1, 2011

By Leszek Hoser

Polycrystalline oxide superconductors that have the perovskite structure, that are oxygen deficient, and that have compositions based. on the so-called. 1-2-3 (YBa2Cu3O7) compound, were investigated.. The materials exhibit a high critical transition to superconductivity at temperatures near 90oK. It was determined that maintaining the oxygen content within the correct range in connection with an appropriate amount of CU ions in the crystal lattice leads to high-critical temperature (Tc:) superconducting properties. High-Tc: superconductors with a critical temperature in the range of 100°K were developed. Further investigations, based. on the theoretical examinations of the origin of superconductivity, have been performed and are discussed..

Jan 1, 1989

By Li Yuhai

Kinetics of non-isothermal precipitate process and crystal growth of perovskite (CaO ? Ti02) phase in CaO-TiOz-Si02-AlP3-MgO system were studied. The experimental results show that the relative volume fraction can be described by the equation given by K. Matusita et at. and the experiential expression of average crystal radius was obtained. The particle coarsening in non-isothermal process has important effects on the crystal growth of perovskite phase.

Jan 1, 2000

By W. Zhao

Several years ago, Reddy and Blander presented upriori model for calculating the sulfide capacity of binary silicate melts. It is modified now to apply to CaO-AlO 1.5 melts at different temperatures and compositions. Our predictions are in very good agreement with the available experimental data. From a comparison of binary calcium aluminate and calcium silicate systems, higher sulfide capacities are obtained in aluminate systems. The sulfur can be removed from hot metal more effectively by adding aluminate melts.

Jan 1, 1995

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

"The design is based on the thermal processing of the wastes in· the intensively bubbled melt in the Vanyukov furnace at the relatively high temperatures (1350- 1450 °C), In this case: -the secondary wastes are not formed; - the especially toxic substances at the outlet from the furnace are absent. The technology was tested on a large scale (on semicommersial bases). Technical and economical basis show profitability of recovery complex for processing of hard garbage waste (HGW) using this technology: the period of capital, investments refunding for the, recovery, complex construction with process annual capacity of 240 thousands tons of wastes is 1,5-2,5 years,"

Jan 1, 2000

By Daoxin Wu, Zhong Cao, Yan Shi, Yu Ding, Huanli Yang, Zhongliang Xiao

"2-substituted benzimidazole-zinc and 2-substituted benzimidazole-copper complexes were main components of organic solderability preservative (OSP) in PCB producing process and affect the thermal stability of OSP film. So these four complexes were prepared by 2-substitutedbenzimidazole reacting with zinc ion and copper ion, the complexes crystals were determined by IR, its thermal stabilities were studied by TG method. The results indicated that the thermal stability of 2-substituted benzimidazole-zinc is higher than the 2-substituted benzimidazole copper,and the thermal decomposition mechanism was presentedIntroductionImidazole compounds which is an important heterocyclic compound shows the important value and outstanding prospects[I-3l in field of biological engineering, medicine, and high-performance composites. It's said that imidazole compounds is an excellent new metal surface treatment[4] agent, because it has good reaction activity with metals and can form a chemical layer on the metal surface. The complexes of imidazole were main components of organic solderability preservative (OSP) in PCB producing process and affect the thermal stability of OSP film. The mechanism of imodazole combined with metal and film deposited has been reported, but the opinions about thermal stability of film have bifurcation, let alone the thermal decomposition mechanism of film at high temperature. The complexes were prepared by combining of 2- substituted-benzimidazole with zinc and copper iron, which were studied by IR and TG method, in order to get thermal stability of different complexes."

Jan 1, 2011

By M. del C. Ruiz

The extraction of Nb and Ta from a columbo-tantalite of San Luis, Argentina, is being studied by using a pressure reactor and HF as leaching agent. The reagents and products have been characterized by several techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), X-ray fluorescence (XRF), X-ray difracction (XRD), surface area (BET) and size particle analysis. Experimental results have shown that the extraction of niobium and tantalum increases with increasing temperature, reaction time and acid concentration. For particle size between +80 and -355 mesh no significant changes are detected. It is also slightly affected by the stimng speed. XRD analysis of the residues did not show formation of new crystalline structures.

Jan 1, 1999