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By M. Misra

The bacterium?Mvcobacterium Phlei has a demonstrated potential to be used for the flocculation of a variety of finely divided minerals. The microorganism possesses both hydrophobic surface and high negatively electrostatic charge. It can adhere to many mineral surfaces ?if the charge and hydrophobic interaction? between the microorganism and the minerals are favorable to adhesion. Experimental results showed that the dolomitic phosphate slime from Florida and fine hematite can be :readily flocculated from dilute suspension.. In the case of dolomitic phosphate slime, a consolidated sediment containing 24'-25 weight% :solids can be obtained from .a dilute slurry .in a short time. Sediments obtained from hematite flocculation are rather massive and more .consolidated than phosphate slime. Mycobacterium Phlei has a specificity for selective flocculation of hydrophobic fine coal particles from pyrite and ash containing minerals. Because of mutual hydrophobic interaction of coal and Mycobacterium Phlei, it was noticed that coal particles appear to be strongly held in the aggregate by adhesion or bridging of bacteria. However, Mycobacterium Phlei is not a good flocculant for either associated pyrite or ash present in coal.

Jan 1, 1991

By S. N. Lekakh

Experimental work and thermodynamic simulations of cast iron refining were carried out using various additions of alkali and rare earth metals. The refining reactions for sulfur and oxygen removal were studied for melts treated with Mg, Ca, and Ce. The measured data and the results of the computer simulations were in agreement. Experimental kinetic data, together with the thermodynamic calculations, were used for optimization of the amount and sequence of the addition of nodulizers for ductile iron production.

Jan 1, 2009

By M. Rosales

By a physical and mathematical modeling, the behavior of the tri-dimensional waving, and the movement of the gases at the Teniente Converter was studied. The mathematical model considers the condensed phases of white metal and slag, along the gas phase, and includes the k-e model for the turbulence description. Both the physical model and the mathematical model allow to conclude that from a fluidynamic stand point the Teniente Converter clearly can melt 3000 tpd of concentrates. Also, both models are suitable to predict the slag fluidynamics and its spacial distribution inside the Teniente Converter, and the splashing in the tuyere zone as well.

Jan 1, 2006

By Heikki Jalkanen

Oxygen converting of hot metal (LD/BOF) is contemplated as an object of simulation. Oxygen converting is a highly complex thermo-chemical process comprising a series of matter and energy transformation and transportation steps that makes the simulation very challenging. The basic principles of CONSIM 5 oxygen converter simulator are presented. Simulator is a comprehensive combination of a physical model with several empirical submodels describing all properties and processes that affect the final result of a converter blow, final mass and composition of steel, slag, dust and converter gas as well as the end temperature of steel. CONSIM simulator is used for simulation of series of high and low carbon steel blows. Simulated steel temperatures, oxygen consumption, blow time and iron oxide content of slag are compared with measured values. Problems of simulation and requirements for quantitative simulation of oxygen converter process are discussed.

Jan 1, 2006

By Ryokichi Shimpo, Akio Fuwa

"In order to elucidate the present status of process-control technology, survey study has been made on the present process control schemes of representative copper smelting and converting processes in Japan. Conceptual control flow diagrams have been deduced and shown on respective functional reactors, i.e. drying, smelting, converting and fire-refining units, where the objective OUTPUT items are correlated to the INPUT variables through respective CAUSE-AND-EFFECT RELATIONSHIPSFuture view has been also discussed on several feasible and desirable improvement and refinement ~n measurements and control system for better copper smelting and converting operations.INTRODUCTIONIn other to seek for the better and efficient operation in copper smelting and converting process, survey study has been first conducted on the present process-control schemes of respective functional unit processes, i.e. drying, smelting, converting and refining unit processes, of representative copper production processes in Japan. Conceptual process flow chart of control scheme has been then deduced where output items are correlated to input items through the respective cause-and-effect relationships.After this survey study, future view has been discussed on the feasible and desirable improvement and refinement in the measurement and control system in these processes. Emphasis has been placed on the better and precise measurements of temperature, oxygen partial pressures in respective furnaces and end-point in converting and refining unit operations."

Jan 1, 1989

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 Li. Jiarong, Zuojian Liang, Qingyan Xu, Baicheng Liu, Shizhong Liu, Hailong Yuan

Single crystal solidification of turbine blades is a key technology for the production of reliable and high efficiency gas turbines. The solidification process of single crystal investment castings causes a number of problems that have to be solved such as the increase of casting defects and complexity of production process. Computer modeling and simulation is helpful to predict the defects and improve the process design. In the paper, a mathematical model for three dimensional simulation of solidification and single crystal growth of investment castings was developed based on CA, mechanism of crystal growth and basic transfer equations such as heat, mass transfer equations. Many factors including constitutional undercooling, curvature undercooling and anisotropy, which had vital influences on microstructure evolution, were considered in the model. Temperature, crystal growth interface and structure defects of investment castings of single crystal superalloy were investigated at withdrawal rates of 4.5mm/min and 7mm/min. Simulated results showed that microstructure evolution and structure defects were predicted reasonably and calculated results were coincident with experimental ones. The study indicated that three dimensional solidification simulation technique is a powerful tool for understanding the fundamental of solidification and the formation of structure defects in single crystal investment castings and finally for optimizing process design.

Jan 1, 2004

By Mahesh C. Jha

Molybdenum, a major refractory metal, is widely used as an alloying element in steels and superalloys to improve their corrosion resistance, physical properties and mechanical strength, particularly at elevated temperatures. The current worldwide production and consumption is estimated at about 130,000 tons contained molybdenum per year. Molybdenum occurs in nature as molybdenite mineral and is recovered by a flotation process as a primary concentrate at molybdenum mines and as a byproduct concentrate at copper mines. The concentrate is roasted to a technical-grade molybdic oxide (tech oxide) in multiple-hearth roasters. About 80 percent of the tech oxide is sold, as such or after conversion to ferromolybdenum, for addition to iron and steel. The remainder is further refined to pure oxide and molybdate chemicals that are used in the manufacture of catalysts, specialty chemicals, molybdenum metal and superalloys. This paper discusses the various steps in the extractive metallurgy of molybdenum, from flotation of sulfide concentrate to reduction of pure oxide to molybdenum metal.

Nov 26, 1999

By J. P. Constantinea

The use of fluidized beds for the roasting of zinc sulphide concentrates marked a milestone in the electrolytic production of zinc. Stable operation of a fluidized bed for zinc roasting requires a particle size distribution that minimizes the risk of defluidization and helps control carryover to manageable levels. However, the understanding of the roasting process is limited, and changes in operating conditions mainly rely on intuition, experience, and trial and error. A research program has been initiated at UBC to study the phenomena that influence the particle size distribution of fluidized bed zinc roasters. In preparation for the experimental phase, this paper reviews the current literature on the phenomena that affect the particle size distribution during fluidized bed roasting and other fluidized bed processes.

Jan 1, 2002

By Mariola Saternus

The quality of the liquid metal has the biggest influence on the quality of the final products. In the metallurgical industry, and especially in aluminium production the refining process is the important technological stage. Today the most popular are refining reactors with impellers like URO ? 200, which can generate small gas bubbles. A rotary impeller also makes the metal bath to be stirred well. There are two basic hydrodynamic parameters: the flow rate of refining gas and the mixing of refining gas (impeller rotation) that influence metal stirring and generating small gas bubbles. The paper presents the influence of the flow rate of refining gas on the hydrogen removal process from aluminium (final hydrogen concentration), taking into consideration the refining process of AlSi7Mg alloy and using URO - 200. The mathematical model of this process is also presented. The equation needed for calculation of the final hydrogen concentration as a function of the equivalent bubble diameter is shown. Basing on this equation the calculations of bubble diameter and optimal refining time are done. This paper presents the physical model (the water one) of aluminium refining process and the gas dispersion taking into account the fact that the gas flow rate is changing from 2,5 to 17,5 l/min and the impeller speed is changing from 0 to 400 rpm. Schemes of gas dispersion in liquid metal in comparison with the model data are shown and the optimal values of the gas flow rate and the impeller speed are chosen.

Jan 1, 2006

By J. W. Dini

Introduction The mission of the Materials Fabrication Division (MFD) is to provide fabrication services and technology in support of all programs at Lawrence Livermore National Laboratory (LLNL). MFD involvement is called for when fabrication activity requires levels of expertise, technology, equipment, process development, hazardous processes, security, or scheduling that is typically not commercially available. Customers are encouraged to utilize private industry for fabrication activity requiring routine processing or for production applications. MFD is .a large diversified service organization including approximately 400 full time employees. The group provides a wide variety of processes including all common machining and fabrications operations, laser and water jet cutting, electrical discharge machining, lapping, electron beam and laser welding, vacuum brazing, heat treating, forming, electroplating and metal finishing, optical polishing and grinding, vacuum coating, vacuum engineering and a variety of plastics operations. These operations occupy more than 1,250,000 square feet of floor space. For more detail on the many fabrication related services available from MFD, see Reference 1.

Jan 1, 1992

By Dhanesh Chandra

In this symposium, research in the area of energy conversion is presented. This symposium has special significance, as we honor three prominent scientists from hydrogen storage research and development field. In this symposium, the majority of papers presented by international scientists and engineers are in the area of hydrogen storage. Other energy conversion papers include magnetic materials, superconductors, and thermal energy storage materials. Recent developments in light-weight high gravimetric hydrogen density hydrides have led to potential use of hydrides for onboard automobile and other applications. This, of course, is significant from environmental concerns of CO2 and other emissions from the current use of carbon based fuels in automobiles. Thus, it is becoming increasingly important to switch to cleaner alternative fuels such as hydrogen [1]. The Challenge of Vehicular Hydrogen Storage as potential hydrogen energy carriers for vehicular applications, with a driving range of approximately 300 miles, require ~5-13 kg of hydrogen stored on-board. In the United States, Centers of Excellence have been established in metal hydrides, chemical hydrides, and carbon-based materials, and abundant scientific and industrial research is being carried on metal hydrides; only some of the current research from the Centers will be reported here. The European commission, Japan Institutions, and others also have numerous hydrogen storage programs in progress. Several international collaborations have also begun between IEA and IPHE scientists to accelerate the progress of development of practical hydrides. A summary of the abstracts is included in this overview.

Jan 1, 2006

By John Anawati

Bauxite residue is an environmentally unfriendly byproduct of alumina manufacturing, produced worldwide in large quantities. This material contains 50– 100 ppm of scandium, a critical material for the production of stronger, weldable, corrosion resistant, and heat tolerant aluminum products. Aircraft manufacturers are particularly interested in Al–Sc alloys because of its ability to form weldable alloys that could potentially reduce aircraft weight by 15–20%. Because of its abundance and low cost, bauxite residue has the potential to be used as an efficient feedstock for valorization processes to recover its scandium content, while in turn degrading this problematic waste. In this project, we developed an efficient process to recover scandium and rare earth elements from a Canadian bauxite residue with high extraction yields, using industrially scalable and economical techniques. The process employs a modified version of sulfuric acid leaching and subsequent impurity removal by selective precipitation. This article outlines the current progress and design rationale in the development and optimization of this innovative and sustainable recovery process.

By J. B. Vander Sande, I. G. Solórzano, B. S. You, P. M. Jardim, W. W. Park

"Alloys with six different compositions in the system Mg-Ca-Zn were produced by melt spinning. The aging behavior of alloys was investigated by measuring the changes in microhardness after isochronal aging and the microstructure was analyzed by means of transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM). All six compositions in the as-solidified condition show a difference in microstructure between the wheel contact side (zone A) and the free surface side (zone B) as a result of the differences in the solidification rate across the ribbons. One of the alloys (Mg-l.5wt%Ca-6wt%Zn) was chosen to be more deeply investigated in this work as it exhibited grain boundary films and an age hardening behavior was produced in that alloy.IntroductionMagnesium is the lightest of all the commonly used metals, and very attractive for applications in transportation. It also has a number of other desirable features, including good ductility, better damping characteristics than aluminum, and excellent castability. However, there are some negative features, such as high reactivity in the molten state, inferior fatigue and creep resistance as compared to aluminum, poor corrosion resistance and high production cost.In recent years there has been a significant increase in magnesium use as a structural material. These structural applications include aerospace, automotive and nuclear industries as well as appliances and sporting goods (1 ). According to reports on Mg-Zn alloys, the addition of Zn (2) in magnesium increased strength. Also, since the maximum solubility of Zn in magnesium is 6.2wt%, a considerable amount of Zn can be retained in solid solution in magnesium alloys by rapid solidification. In addition, Ca is known (3) to be one of the most potent alloying elements for refining the microstructure and precipitates in magnesium alloys, and also to improve mechanical strength and corrosion resistance."

Jan 1, 2000

By R. Nilsson

In the present work the sulphide capacities of Ca0-Mn0-Si0, ternary slags have been measured in the temperature range 1798 - 1873 K by equilibrating the slag with a gas-mixture containing CO, CO,, SO, and Ar. The results are compared with the data reported in literature. A theoretical model has been developed in the present work where the sulphide capacity is expressed as a function of the slag composition and temperature. The model enables the estimation of sulphide capacities of complex slags with a knowledge of the capacities of simpler systems.

Jan 1, 1994

By Mamoru Kuwabara

A high-power sound which can transmit through any continuous elastic medium with less attenuation, particularly in liquid allows us to externally control the system of concern by using the acoustic radiation force or the cavitation phenomena. These functions may eliminate gravitational and/or atmospheric constraints which are often encountered in conventional operations for producing clean and advanced materials. This paper outlines the recent development in the field of sonoprocessing of materials. Cold model experiments in some vessels have been performed to simulate ultrasonic operations such as inclusion removal from liquid, degassing of melt, emulsification of two liquid phases, solidification processing, and decomposition of chemical species in waste water. High speed visual imaging is carried out for better understanding of the cavitation phenomena as well as the followed microjets during the processing. The radiation force acting on fine suspending objects in a fluid can be utilized for eliminating or rearranging/orienting the objects in the fluid. Acoustically induced cavitation phenomena in liquid can be utilized as an effective dynamic means to control interfacial phenomena as well as micro- and macro-mixing of liquid. Sonochemical and thermal effects in cavitation multi-bubble can be also useful in a waste water treatment.

Jan 1, 2006

By C. D. Chapman

Current regulations regarding the landfill disposal of asbestos containing wastes are inadequate to ensure there are no ground water or airborne emissions. Accordingly, there is growing recognition that asbestos wastes can only be safely disposed of by using techniques that destroy the hazardous fibres. An innovative high-temperature plasma arc technology (The MAGRAM Process) is being developed for the recovery of magnesium metal from asbestos together with supplementary magnesia containing feedstock. The furnace will operate in. open bath mode with aluminium and/or ferrosilicon being employed as reductant. An important advantage of the process is that magnesium vapour within the furnace will be generated close to atmospheric pressure rather than at reduced pressure under which existing processes operate. Thermodynamic modelling work has been undertaken to define the range of slag composition and furnace temperature under which magnesium production at atmospheric pressure is feasible. The effect of slag chemistry, reductant addition, and temperature on product quality and yield have also been investigated and key aspects have been tested on bench scale. A 300 kW pilot plasma furnace unit has been employed for the treatment of calcined asbestos wastes. Aspects of design and operation of the unit are detailed. Acknowledgement: This work is substantially financially supported by the European Communities under the Industrial and Materials Technologies (Brite EuRam H) Research and Development programme.

Jan 1, 1995

By Gabriel Riveros, Ariel Balocchi, Andrzej Warczok, Daniel Smith

Blister copper from converting of copper matte is processed by fire refining prior to electrorefining. The fire refining consists of two steps: copper oxidation with impurities slagging and copper reduction. The classical batch process is carried out in vascular or reverberatory furnaces called anode furnaces. A new process for continuous copper fire refining has been proposed. The copper flows through two reactors in cascade, where is oxidized and reduced. The flow of a liquid copper through a ceramic packed bed increases the surface area and the rate of oxidation as well as the rate of reduction in the packed bed of charcoal. Mathematical modelling allowed for the design of a laboratory scale demonstration installation and industrial-pilot installation in Hernan Videla Lira Smelter (Paipote). The results have demonstrated the process feasibility and flexibility in operation.

Jan 1, 2009

By M. G. Basavaraj, S. Sarkar, G. S. Gupta, P. D. Patil

"Previous experimental study on raceway size hysteresis on two-dimensional cold model showed that the inter-particle and wall-particle friction had a very large effect on the raceway size. Existing literature correlations for raceway size ignore the frictional effects. It has also been shown in the present study that their applicability to the ironmaking blast furnace is questionable. To take into account the effect of friction on the raceway size a stress analysis has been done for the raceway region. Two-dimensional fluid flow equations under turbulent conditions have been developed and solved computationally in order to get the pressure forces. The frictional forces were obtained in terms of stresses. To predict the raceway size a force balance was done for the raceway zone considering the pressure force, the frictional force and the bed weight. The resulting equations from the force balance are able to describe the raceway hysteresis phenomena reasonably well along with the raceway size. A two dimensional experimental set up has been fabricated in order to validate the computer predictions. Predicted values agree well with the experimental values.IntroductionWhen a high velocity blast of air is introduced into a packed bed through a tuyere, a cavity is formed in front of the tuyere. This cavity, formed in the iron-making blast furnace, is called the raceway. Coke tumbles down and bums in this raceway, generating heat and reducing gases for the iron-making process. The raceway is responsible for producing most of the reducing gasses in the blast furnace. In addition, the size and shape of the raceway determines the movement of solids within the blast furnace, the distribution of gases and liquids (slag and metal), setting the location where the primary chemical reactions occur and the temperature profile in the lower part of the blast furnace.Due to the importance of the raceway, many investigators l - 6 have studied it and have predicted the raceway size using the empirical correlations based on experimental (hot & cold) and mathematical models. A number of correlations have been reported in the literature to predict the raceway size by various investigators3 - 6 which are different to each other. Each of the correlations shows a different dependence of raceway diameter (DR) on bed height, particle size, solid density, bed voidage and blast velocity. None of the correlations includes the effect of solid stresses on the raceway size and shape. The magnitude of these stresses will depend on the bulk solids properties (internal angle of friction, wall angle of friction) and the bed dimensions."

Jan 1, 2001

By Shunhong Huang

To improve understanding the effect of heavy metal chromium on soil biota, laboratory incubation experiment was carried out in the soils contaminated artificially with five concentrations of chromate (50, 250, 500, 1000 and 2000 mg kg_1 soil) over time (35 days). The population and diversity of bacteria, fungi and actinomycetes in soils were measured as indicators of soil microbial processes in the disturbances mentioned above. Incubation experiment results elucidated that the population and diversity of microorganisms decreased with increasing Cr (VI) concentration. Furthermore, various microorganisms showed different sensitivity to total Cr contamination. The sensitivity of microbial population to chromium contamination was in the order: actinomycetes >bacteria>fungi. The resulted implied that the microorganism can be used as an indicator of chromium contamination.

Jan 1, 2008