Search Documents

By R. K. Mehta

Microorganisms have been increasingly used in applications such as-metal solubillzation, precipitation and recently being used as flocculants. Optimal control and on-line monitoring of these processes occurring in microbial reactors are of extensive interest but often difficult because of the unavailability of a mechanistic model of the process and on-line direct sensors. In this paper a dynamic populatlon balance model of microbial desulfurization will be presented. The influence of certain physical and biological parameters on the leaching rate will be illustrated via computer simulations and an extended continuous-discrete Kalman filter will be Implemented for estimation of unknown states.

Jan 1, 1991

By Michael L. Sorokin

The various methods of converter slag cleaning operation are analysed from the thermodynamk point of view: cleaning using coal, cleaning using combustion products of natural gas and cleaning in presence of matte. All calculations were done, applying the developing computer procedure based on the free energy minimisation algorithm. Three-suffix Margules equations were used to calculate thermodynamic properties of melts; The calculations resulted in recommendations for the practical appliance.

Jan 1, 1995

By J. Jakumelt

The coupled simulation of mold filling and solidification for an investment casting process presents difficult. This is due to the complexity of the carious physical process and the geometry, To achieve this task in a precise way, the CFD program FLUENT and the casting simulation tool CASTS were closely coupled. Any physical quantity, such as velocities or temperatures, can be exchanged via files after each time step of the simulation. The communication and operating sequence of the programs is controlled by PERL-scripts. This enables the expertise of FLU ENT for flow simulation and the strength of CASTS, for casting simulation to be combined. The coupled simulation was successful applied to an aerospace investment casting. Several physical models were tested for correct treatment of the casting filters, the porosity of the mold and the viscosity of the liquid metal. The results demonstrate that even complex investment casting geometries can be investigated using CASTS-FLUENT.

Jan 1, 2003

By M. Zamalloa

Slag foaming is an important phenomenon in many metallurgical processes. It creates large surface areas for multi-phase reactions to take place. In other applications, it protects electrodes and improves the energy efficiency by reducing radiation from hot surfaces. However, it may also be a source of serious disturbances. To control and optimize the use of slag foams, an extensive knowledge of the factors controlling the foam formation and stability is required. Slag foaming experiments were carried out using synthetic FeO-CaO-Si02 slags at temperatures ranging from 1200 to 1350 "C. A data acquisition system was used to continuously measure the foam height, gas flow rate, bubble frequency and temperature. The experimental results show that the gas injection rate has a strong effect on the behaviour of slag foams. At high flow rates and rapid bubbling, unstable foams with short decay times were created. The addition of P20, favours the foam formation and stability by lowering the surface tension of the slag. The average foam life increases with decreasing basicity (CaO/Si02). It is proposed that this is attributed to the increase of the surface viscosity due to surface adsorption of a thin film of silica, retarding the drainage of the liquid films.

Jan 1, 1992

By J. Schmidl

In non-ferrous metallurgy the service life of refractory materials typically ranges from several weeks up to three years or more and is strongly dependent on operating conditions. To support our customers with the most viable refractory solution for their needs RHI Magnesita follows a structured approach of thermo-chemical calculations, experimental evaluation from lab scale up to industrial field tests and post-mortem analysis of used refractory materials. This paper will give an overview of the RHI Magnesita refractory selection process and the most recent developments of the experimental setup for the so called HF-IF test. This is a dynamic corrosion test that allows to determine fundamental properties of different refractory material types under process conditions subjected with respective customers process materials. The HF-IF experimental procedure is an excellent tool to simulate refractory wear in industrial processes, diminishing risks associated with plant trials and support decision making to choose the optimal refractory solution for the customer.

By Henrlk Gripenberg

To solve the environmental and financial problems of the traditional Rotary Salt Furnace process, a new salt-free method for aluminum dross and scrap melting, ALUREC, has been developed by AGA and its partners, Hoogovens Aluminium and MAN GHH. AGA and Hoogovens Aluminium developed the main process concept and jointly carried out trials on pilot plant scale. Owing to excellent results" the partners decided to jointly erect a commercial scale test plant. The order for the design and erection of the furnace went to MAN GHH. The three companies designed the test plant and began operation in the spring of 1994. The results have been excellent and the process is expected to be a technical and commercial success.

Jan 1, 1995

By M. Jahazi, P. P. Bhattacharjee, K. Chadha

The present work investigated the effect of strain reversal during high pressure torsion on the evolution of microstructure, texture and hardness properties of two different materials with different dynamic recovery behavior, namely, high purity (99%) Aluminum (2N-Al) and Aluminum-Magnesium (Al-2.5%Mg) alloy. In the two aluminum alloys subjected to different routes, the evolution of the ultrafine structure followed same trend. At lower strain level, sub grains with prominent LAGBs network were observed and at higher strains, ultrafine equiaxed grains separated by HAGBs were observed throughout the disk. The texture evolution in monotonically and strain reversal processed 2N-Al and Al-2.5%Mg showed presence of typical torsion texture components at different strain levels. The strength of the components was observed to follow different trends depending on the processing routes.

Jan 1, 2015

By Junfu Chen, Jiann-Yang Hwang, Yong Zhou, Lijun Lu, Likun Lia, Jixiong Liu

The sheet-like NiS-ZnS heterostructured composites were prepared by the microwave hydrothermal. The fabrication of the heterojunctions broadened the range of light response of ZnS. The photoexcited electrons of ZnS migrated to the redox potential of NiS/Ni2S under visible light irradiation, which can facilitate the effective separation of photogenerated electrons and holes in space. The visible photocatalytic activity towards hydrogen production for NiS/ZnS nanosheet heterostructed composites without co-catalyst achieved 0.28 mmol h–1, and the quantum efficiency was up to 18.6% under the wavelength with 420 nm visible light irradiation.

Jan 1, 2015

By Alicia E. Ares, Carlos E. Schvezov

In the present work it was observed the nucleation and growth of grains in the equiaxed zone of metal matrix composites (MMCs) samples directionally solidified wit the presence of columnarto- equiaxed transition (CET) in the samples. In order to do so, first, it was defined the difference between the real temperature at a given instant, which it is used in the analysis, its variation and furthermore, the variation in the solid fraction with time between the beginning and the end of solidification. It was determined a growth law assuming a lineal variation of equiaxed grain radius as a function of time, and also, it was expressed a law of grain density as a function of time, considering the presence of SiC and Al2O3 particles in the matrix. Finally, the results obtained were validated with measured values of grain density at each position of the thermocouples in the equiaxed zone of the solidified samples.

Jan 1, 2015

By Jun Li

Rate processes of silver cyanidation were studied with the objective of understanding the reaction mechanism. The research was divided into three sections: anodic dissolution of silver in cyanide solutions, cathodic reduction of oxygen on silver surfaces and the direct leaching of silver in oxygenated cyanide solutions. The charge transfer steps plus the diffusion of reactants from bulk solutions to the silver surface were identified as rate-limiting and the rates of both anodic and cathodic reactions can be calculated using the Butler-Volmer equation and Fick's first law. Based on mixed potential theory and the results of electrochemical studies, a comparison of the rate obtained from direct leaching with that predicted from the calculation is made. Calculated results agree well with the experimental data.

Jan 1, 1992

By L. Katgerman, R. Van Toi, H. E. A. Van den Akker

"Mould filling simulations are powerful tools for optimizing the characteristics of castings. The robustness of calculational methods for mould filling simulations is generally tested in simple geometries. While a vertical plate has been used often for validation studies, this paper aims at mould filling simulations of a horizontal thin wall casting. Such castings exhibit a strong interaction between heat transfer (solidification), surface tension and gravitational force.The results are presented of a study to validate numerical simulations of mould filling phenomena in a thin wall horizontal casting. Solidification during mould filling is studied computationally. Velocities are measured using Particle Image Velocimetry.INTRODUCTIONIn foundry practice Computational Fluid Dynamics (CFD) is being considered a promising tool to arrive at a better understanding of casting defects introduced during the mould filling period of a casting. The use of CFD is believed to be advantageous in predicting possible defect locations, pouring times, and the lowest possible casting temperature without the risk of cold shuts. In addition, CFD may be used to optimize pouring system geometries [1,2]. As opposed to experimental studies in, e.g., cold water models, CFD allows for the flexible modification of the casting geometry and the pouring system, and for the inclusion of physical effects such as solidification and heat transfer. Thus, a proper use of CFD may lead to a reduction of the casting rejection rate without expensive trial-and-error procedures, and to a decrease of production costs in foundries. Mould filling simulations take a special place in CFD, because a free surface tracking algorithm is required. Over the past decade methods, MAC [3] and SOLAVOF [4], have been extended to 3-D. The robustness of computational methods for mould filling simulations is generally tested in simple geometries [5,6]. While a vertical plate has been used often for validation studies, this paper concentrates at mould filling simulations of a horizontal thin wall casting. Thin wall horizontal castings exhibit a strong interaction between heat transfer (solidification), surfaces tension and gravitational force. The gravitational force in this setting is orthogonal to the plane of flow and has therefore no influence on the shape of the free surface in the plane of flow. Mould filling numerical methods and algorithms have been recently reviewed by Chen et al.[7]."

Jan 1, 1999

By Andreas Orth

Outokumpu Lurgi Metallurgie has developed a process for the calcination and reduction of laterite nickel ore tines where the reduction of iron and nickel to the wustite/metallic states respectively, is performed in a fluidized bed reactor using reduction gas generated very cost effectively from natural gas in an autothermal catalytic reactor. As an option coal can be used as reductant as well as additional fuel. The process of reduction and calcination is very energy optimized. It uses the off gas from the fluidized bed reduction reactor, which still contains energy, to dry and calcine the nickel ore fines in a primary stage circulating fluidized bed (CFB) reactor. The product shows high metallisation of nickel and iron oxides reduced to the wustite stage. This results in considerable energy savings in smelting the prereduced product to ferro-nickel. Alternatively the product can be leached to produce nickel. Laboratory tests showed very high recovery of nickel and cobalt. Keywords: Fluidized Bed, Prereduction, Calcination, Ferro-Nickel

Jan 1, 2004

By Steven I. Baskin

Cyanides are utilized in many industrial applications including preparation of chemical intermediates, electroplating, and' mining, Cyanide has been utilized in chemical warfare operations as well Cyanide is also synthesized and found in plants and animals including man where it is thought to perform multiple functions. A variety of enzymes are known to detoxify cyanide under different conditions. These include rhodanese, 3-mercaptopyruvate-sulfur transferase, thiosulfate reductase, cystathionaseand albumin. Cyanide appears tQ exert its toxic effect primarily by inhibiting cytochrome oxidase? although other enzymes are also inhibited. Therapeutic antagonist categories to treat cyanide include methemoglobin formers such as nitrite, sulfane-sulfur donors such as thiosulfate, metal salts or complexes such as cobalt and cyanohydrin-forming compounds such as dihydroxyacetone or alpha keto-glutaric acid. Advantages and disadvantages of each category will be discussed. Newer compounds under development have been found that may allow for prophylactic therapy for cyanide poisoning with minimal side effects; In addition, portable co-oximetry devices may provide real-time measurement of cyanide in field units.

Jan 1, 1998

By Cang Daqiang, Li Yu, Liu Xiaoming, Zong Yanbin

"Utilization of high-quality heat in melting slag is a great challenge for iron and steel industry. In the paper, a new method is put forward to concurrently utilize heat and slag by converting the melting slag directly into high valued materials, slag glass-ceramic. A glassceramic with a higher basicity of 0.7 than traditional basicity of 0.45 was prepared from steelmaking slag in order to utilize more hot melting slag. Effects of Alz03 on its crystallization processes were researched by XRF, DTA, XRD and SEM. Results show that Alz03 in glassceramic would have great effected on its property. When the Alz03 content ranges within 12%-15%, glass-ceramics with basicity of0.7 could reach the best performances. The change of dominant phase in glass ceramics from akermanite and wollastonite to akermanite and gehlenite would significantly degrade its mechanical property. An increase of Al2O3 content leads to a rise of the viscosity and crystallization activation energy of the glass, while results in increasing sintering temperature and crystallization temperature of glass, which contributed to its fully crystallization and densification process.IntroductionSteel slag is a by-product under a process of converting iron to steel at above 1600°C, and 0.1-0.15 ton molten steel slag would be discharged for producing per ton of steel in the process. The discharged steel slag at 1600°C has heat of 68 kgce/t. In 2012, China's steel output reached 716 million tons, and produces about 100 million tons of steel slag and 68,000 tee of heat in it [1,2]. But at present, utilization of both slag and its heat at 1600°C is a great challenge for iron and steel industry.Dry granulation of melting steel slag by air and then recovering the heat of the hot air are a traditional technology which have not yet been put into practice for very low heat conductivity of the slag and low efficient of heat exchange among the different processes [3,4]. Therefore, a new method for high efficient utilization of both steel slag and its high temperature sensible heat is put forward [5,6], which is on-line reducing and extracting iron from molten steel slag and then directly preparing glass-ceramic by use of the residual molten slag."

Jan 1, 2014

By Jozef Zmik, Sergey Dobatkin, Martin Fujda, George Raab, Libor Kraus

"The present work, likewise, deals with grain refinement of medium carbon steel AISI 1045 having different initial microstructure resulting from thermal and/or thermomechanical treatment (TM) applied prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain Eef ~ 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 µm and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. The microstructure development was analyzed in dependence of effective strain introduced ( Eef ~ 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrains and submicrocrystalline grains having high angle boundaries. The intensive straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The lamellae cementite spheroidization was more extensive in TM treated steel samples. The deformation behavior of for both steel structural state confirm the strength increase; however the work hardening behavior was modified with respect to initial structure of steel prior SPD processing.IntroductionIn the last years, ultrafine grained materials have attracted considerable research interest because they tend to possess high strength without sacrificing toughness and ductility. Microstructural refinement of steel is usually achieved by alloying and/or by thermomechanical treatment process, which modifies phase transformation. Recently, advancement of severe plastic deformation (SPD) techniques provides another efficient access for grain refinement of metals and alloys. The fabrication of bulk materials with ultrafine grain sizes has attracted a great deal of attention over the past two decades because of the materials' enhanced properties [ 1, 2]. In last decade a worldwide effort in manufacturing process to obtain ultrafine grain structures in steels is persisting."

Jan 1, 2011

By Takashi Araki

In this work, we have elucidated the two-step oxidative reaction mechanism of 2,4,5-trichlorophenol by adsorbing oxygen atom for oxidative decomposition reaction of 2,4,5-trichlorophenol on oxide catalyst surface using ab initio molecular orbital calculation. In the first oxidation, total energies of reaction products have been shown extremely stabilized at all oxidation positions. This reaction occurs due to charge transfer from benzene ring to adsorbing oxygen atom. As a result, ? bonding of benzene ring are weakened. However, the benzene ring of 2,4,5-trichlorophenol does not perform cleavage reaction. In the second oxidation, the benzene ring of 2,4,5-trichlorophenol can perform cleavage reaction, since the second oxidation obtains larger stabilized energies than the first oxidation.

Jan 1, 2003

By Robin D. Rogers

Room temperature ionic liquids (RTIL) can replace certain traditional organic solvents in liquid/liquid extraction of metal ions from aqueous systems. The very low vapor pressure and non-flammable nature of RTIL warrant consideration of these neoteric solvents for new processing technologies which will reduce pollution, Increase safety, and lower costs. Metal ion separations in RTIL, however, will typically require the use of an extractant and research is needed to identify suitable selective extractants which have appreciable solubility in the RTIL and low solubility In the aqueous phase. Choice of extractant should also take into account the toxicity, expense, and disposal of the ligand.

Jan 1, 1999

By Hylton McWhinney, Doanh Tran, Jewel Andrew Gomes, George Irwin, Sameer Pallavkar, Md Islam, David Cocke, Mohammad Rafiqul Islam

"High-performance nickel-based nanocrystalline zinc oxide adsorbents have been prepared adjusting Ni/Zn mol ratio of 1 :5 by thermal decomposition, coprecipitation and sol-gel method for selective adsorption of thiophene in liquid hydrocarbon fuels at ambient temperature and pressure. To understand the nature of reactive adsorption of thiophene (C4H4S) on Ni/ZnO, the effect of preparation techniques, morphological and textural structure on the desulfurization activity was investigated. A model fuel (20 mL) consisting of pentane (C5H12) and thiophene was prepared and adsorption experiments were performed by a batch method under ambient conditions. The physicochemical behaviors of the fresh adsorbents were obtained using X-ray diffraction (XRD) with EDAX, scanning electron microscopy (SEM). The sulfur concentration in the mixture was monitored by UV-vis spectrophotometry. The adsorption reaction confirmed that ZnO played a crucial role in taking up S element to convert it into ZnS. The deposition of nickel on ZnO is an innovative approach which takes advantage of the selectivity of Ni towards S-species and the high adsorptive capacity of ZnO support.IntroductionLow temperature deep desulfurization of fuels via selective adsorption of sulfur compounds keeping coexisting aromatic hydrocarbons and olefins intact is receiving increasing attention in the research community worldwide in order to satisfy the upcoming environmental regulations and fuel specifications. The sulfur compounds in the transportation fuels is a matter of concern when global crude oil slate is becoming heavier and sourer and environmental restrictions on both the refining process and the refined products are becoming more stringent. According to the current refinery technologies, the sulfur content in refinery fuel is typically around 300-500 ppm by weight (ppmw) [1-3]. Starting in 2006, sulfur limits in highway diesel and gasoline were set to 15 ppm and 30 ppm, respectively. During combustion sulfur in the fuel are converted to toxic sulfur oxide (SOx) and contributes to air pollution and acid rains [ 4]."

Jan 1, 2011

By Kiyoshi Shibata, Jun-ichi Hayashi

"Steel making technology poses strong potentials for environmental protection in three direction. One is pollution control on steel making process itself. Japanese steel industry has cut down various type of emission drastically since 1970's. Secondary, those process technology can be applied to reduce environmental burden in other industrial sectors. One of the successful examples is municipal waste treatment facility. Thirdly, development of high performance steel products, such as high strength steel for automobile body, can contribute to improve environmental performance during their use, based on the concept of life cycle assessment. Some examples of the successful development and future task is discussed.IntroductionsStack and smoke used to be a symbol of energy intensive industry such as steel making. But, scenery of steel works and its surroundings have been completely changed, and steel products have been changing, as well. The steel making industry consumes huge quantities of energy and resources. Variety of technical development have been carried out to reduce the pollutant release. The steel industry in Japan has been making direct and indirect contributions to reducing of various kinds of environmental impacts through development of high-performance process and products: Its potential technical capability accumulated in steel making is fundamental and essential infrastructure for the vein systems of our society. In this paper, the activity of steel making industry for better environment is discussed"

Jan 1, 2000

By Mark R. Jolly, Jean-Christophe Gebelin, Aleksander Cendrowicz

"Injection of wax patterns is the first stage of the multi-stage process of investment casting. The quality of the final casting and its dimensional accuracy is highly dependent on this stage of the process. Pattern waxes used in the industry behave in a complex visco-elastic-plastic manner. The modelling of such material behaviour is therefore not simple.In this paper a number of configurations of die will be shown in which the injection of the wax has been carried out for a range of processing conditions. Some of the dies are transparent and the movements of wax front observed can be compared with those predicted by simulation. Surface defects in final components will also be shown and compared with the location predicted by simulation software. Some discussion will be presented on the limitations of the software used and the time-scales achieved for practical use as a design tool within the foundry environment. IntroductionThis paper presents the research activities carried out at the University of Birmingham on the modelling and prediction of the behaviour of industrial investment casting waxes during the injection of wax patterns. These research activities are done in the context of a more global study of the fundamental aspects of the investment casting process, the FOCAST project. Regarding the wax injection process, the aim of the project is to achieve a better understanding of the key factors that will lead to better castings. The filling of the die during the injection has been studied. Some other phenomena such as shrinkage/warpage or creep under residual stresses are also studied, but not presented here. Two commercial investment casting waxes have been characterised in order to model their behaviour and predict mould filling and subsequent defects.This paper will present the models that have been used in our work, the simulation packages used, the experiments carried out to validate the modelling and exhibit the defects due to bad filling, and finally the numerical simulation results."

Jan 1, 2001