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By Xiancong Zhao, Hao Bai, Qi Shi, Zhancheng Guo

Reducing electricity cost is important for energy intensive industries such as the iron and steel industry. With the implementation of time-of-use (TOU) electricity price, plenty of attention has been paid to the optimal management of byproduct gases. The time-of-use (TOU) electricity price is the practice of implementing different prices for different times of use. It is possible to reduce electricity cost by adjusting the amount of product gases stored or used for power generation throughout the day. In this paper, a novel mixed integer linear programming (MILP) model concerning the TOU electricity price is proposed to optimize byproduct gas use. Compared with previous models, this model considers the optimal load shift between gasholders and boilers under TOU electricity price. The case study of a steel plant demonstrates that the electricity purchase cost can be reduced by more than 30% after optimization.

Jan 1, 2016

By Wayne Bell, Shivanand A. Borkar, Anish Upadhyaya, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"A refractory ore body located in Michigan’s Upper Peninsula contains high concentrations of nickel and copper chiefly occurring in the minerals pyrrhotite, chalcopyrite, and pentlandite. Refractory ore bodies are difficult to treat by conventional mineral processing methods so microwave pre-treatment of the ore is employed to increase metallic-particle/host rock liberation by making use the differential thermal expansion properties of the mineral phases that absorb microwave energy. The Curie temperature measurement of metallic-bearing particles is in agreement with the known value for pyrrhotite occurring at 325°C. A nickel-rich iron sulfide mineral is found to be in occurrence and also appears to be magnetic under BSE imaging. It is shown the ore particles heat rapidly when exposed to microwave radiation for short durations of time mainly due to the high concentration of ferromagnetic mineral phases. Rapid heating causes thermal expansion of constituent mineral phases that produce cracks within ore particles. SEM imaging shows fracture occurring along grain boundaries and throughout host rock matrix. Ball milling experiments show an increased grindability of the ore resulting in a decrease in work index values.IntroductionCrushing and grinding operations consume 50-70% amount of energy used in mineral processing operations [1]. All these processes involve high energy impact of surfaces to develop compressive stresses that produce cracks to initiate breakage of particles. Microwave pre-treatment of certain types of ore might provide an energy savings to these type grinding processes by taking advantage of the tensional forces produced by selectively heating microwave absorbing type mineral phases. The heating of ore particles produces cracking by thermal expansion of the constituent mineral phases. Conventional heating has been investigated and shown to positively aid in grinding processes but determined energy inefficient to be used commercially."

Jan 1, 2011

By S. M. Copley, M. Yankova, E. Y. Yankov, J. A. Todd

"Nanophased coupled growth structures, with spacings of -10 nm, have been observed in banded microstructures produced by laser melting hypoeutectic Ag-Cu alloys. These coupled growth structures comprised a Cu-rich phase of width - 1 nm and a Ag-rich phase of width - 9 nm. In this paper, microstructural observations of nanophased coupled growth structures in hypo eutectic AgCu alloys are presented. Laser beam velocities for the transition from banded to microsegregation free microstructures are modelled and compared with experimental values. Models are presented to show that, at a critical undercooling, initial growth of a Ag-rich, metastable, extended solid solution is rapid but slows to a halt as copper is partitioned into the liquid at the solid/liquid interface. Following nucleation, the coupled growth structure then grows until the partitioned copper is consumed, at which point growth of the Ag-rich solid solution is again accelerated. This cycle then repeats resulting in banded microstructures comprised of 750 nm of the Ag-rich extended, metastable solid solution, followed by 250 nm of the coupled growth structure.1. Structural Studies of Laser Melted and Resolidified TrailsPresented here are observations of laser melted and resolidified trails in Ag-Cu alloys obtained at beam velocities ranging from 0.7 to 34 cm S·I. When the laser beam is scanned along the surface (positive x-direction) with a velocity Vb a melt pool with the shape given in Fig. 1a moves with the beam. The isotherms move with the velocity, Vi,. = Vb cos.p. Calculations employing the thermal analysis of Kou, Hsu and Mehrabian [1] for the beam velocities of this investigation and for the thermal properties of AgCu alloys, indicated that, .p, the angle between the isotherm velocity and beam velocity should be small at the surface where microstructural studies were made. This prediction was supported by observations of trail cross-sections. Based on these observations, and the calculations which include latent heat effects, the isotherm velocity for observations near the surface in our investigation was taken to be 27 cm S-I."

Jan 1, 1994

By J. Tang, B. Q. Li, R. Akarapu

"An integrated model is developed to represent the three-dimensional electromagnetic wave propagation and thermal phenomena during microwave heating of ceramics and dielectric/biological materials. The model development is based on the edge finite element formulation for electromagnetic fields and the node fmite element formulation for thermal phenomena. Results are presented and compared well with available analytical solutions and experimental measurements. With the model, the effect of sample positions on the electromagnetic and thermal field distributions is studied.IntroductionMicrowave, as an electro-heating source, has been widely used in the processing industries for packaged foods and other materials. The commonly used household microwave oven is a typical example of microwave heating processes. Other industrial microwave processing systems include large-scale microwave guides and cavities, which are used for the sintering operations as required for making ceramic components or for sterilizing the packaged foods."

Jan 1, 2004

By D. Zhao

High temperature deformation characteristics of austenitic 304L, and martensitic 410 and 416 stainless steels were investigated by conducting compression tests over a wide range of temperatures and strain rates (950-1250 C and 0.001-20 s-1). Flow behaviors of the three alloys were characterized. Optical metallography was performed to determine the as-deformed microstructures. The flow behaviors were related to microstructural phenomena during high temperature deformation. Dynamic recrystallization was responsible for the flow softening. Both dynamic and static recrystallization were operating, and the recrystallized grain size increased with increasing temperature and decreasing strain rate. Strain rate sensitivity was found to increased with increasing temperature and decreasing strain rate. No defects such as cracking and shear bands were observed at those test conditions. Preferred processing conditions can be selected by considering as-deformed microstructure and strain rate sensitivity.

Jan 1, 1994

By José Roberto de Oliveira

Based on literature review one can see that the main objectives of MnO reduction is the comprehension of slag interactions and reactions with other elements beyond carbon. That's because it is worthwhile to study pure MnO reduction, where there will be not oxides interaction and just carbon will be the reduction agent. By a thermodynamic analysis we know that Si can react with MnO, then it's important to study this influence, so as Mn content. Our work aims to develop kinetics parameters for the MnO reduction, varying Mn and Si contents in bath. This has been given by pressure measure of CO in a Fe-C bath. The CO is generated by the oxide reduction with carbon. It has been proved that: - Mn content decreases the MnO reduction; - the MnO reduction is mainly influenced by Si content in a bath containing Iron, Carbon and Manganese so as Silicium

Jan 1, 1997

Hazardous waste has often very complicated chemical compositions in a variety of physical forms and is normally processed in rotary kiln incinerators. Due to large variations in waste types and difficulties in feed characterization, the complex transport processes within the incinerator are not well understood, and the incineration process meets challenges in a smooth operation, and expects various uncertainties in the process chemistry and emission control. For better understanding of the incineration process, simulation was carried out by using Computational Fluid-dynamics (CFD) to characterize temperature and species distribution in the incinerator. In order to catch certain aspects of thermal and chemical behavior, a novel approach is proposed to represent approximately the waste streams and the subsequent combustion process. Hazardous waste in various forms from an industrial-rotary-kiln waste incinerator is firstly converted to a hydrocarbon-based virtual fuel mixture with approximately the same HIC molar ratio and calorific value. The simulation of the combustion process of the simplified hazardous waste was proceeded with a combustion model. The distribution of temperature and chemical species especially the remaining CO in the system is preliminarily investigated. Distribution of CO concentration, as a good indicator of emission level for the incineration process, could be used to evaluate the emission control. The predicted temperature distribution has been compared with available measurement data from an operating rotary kiln waste incinerator at AVR-Chieme, in the Netherlands. Reasonable agreement has been reached between the measured and predicted temperature data. In the next step, measurement of species distribution in the system is planned to further validate the combustion model.

Jan 1, 2003

By C. Dresen

This paper discussed the reaction kinetics of the reduction of industrial phosphate pellets for P4 production. In the reduction process of various phosphate ores, the following parameters were investigated: Diffusion of the phosphorus oxide and other gaseous products from the reaction mixture after having been reduced on the reductant (coke) surface. Influence of silica on reaction kinetics. Temperature influence. Influence of mineralogy and morphology (different ores). Particle size influence of silica and coke. Experiments were carried out in a vertical tube furnace with 2 ores, 2 types of silica and one type of coke. Selected experimental conditions simulated furnace conditions. The following conclusions could be made: Reaction rate increases with the addition of SiO2 into the pellet. The reaction rate increases above 1350°C (melting temperature of the slag). Mixing different ore types in the pellets leads to differences in reduction kinetics. Particle size of the coke particles influence reduction kinetics. The amount of slag formation is influenced by silica addition, coke size and temperature.

Jan 1, 2002

By Dewei Zhu

A general purpose computer model for describing the transport phenomena and resulting rate of deposition in Chemical Vapor Deposition (CVD) processes has been described. Partial differential equations describing the conservation of mass, momentum, energy and chemical species are solved by a computer program employing a finite volume method. The program allows for multiple chemical species and natural convection effects. In this paper, the deposition of silicon by the reaction of silicon tetrachloride and hydrogen in a vertical stagnation flow reactor with rotating substrate has been considered. The effects of reactor pressure and substrate rotation speed on the rate and uniformity of deposition have been studied. The predicted rates of silicon deposition along the substrate are in reasonable agreement with experimental results found in literature. The model can be used as a tool for design optimization of such reactors.

Jan 1, 1990

By T. Gunawansa, T. L. Alford, Zhao Zhao, A. R. Lanz, N. David Theodore

Many sustainability issues arise during the manufacturing processes that are currently used for solar cells. Solar energy is a renewable energy source that is independent of the earth’s resources, and it is therefore important for the development of more sustainable technologies. Microwave annealing (MW) has been proposed as a technically feasible fabrication scheme for large area silicon solar cells. Apart from that, microwave annealing has been demonstrated to be a promising alternative for repairing damage and electrically activating dopants in ion-implanted semiconductors for integrated circuit manufacturing. A microwave oven is cheaper than conventional furnace systems. In addition, microwave heating is much more efficient than conventional furnace heating, as heating is directly produced inside the material. This minimizes the loss of energy due to heating of the ambient. There is a need for more efficient processing techniques. In this study, microwave annealing is used as an alternative to the current postimplantation processing. Arsenic-doped silicon was microwave annealed (with an aluminacoated silicon carbide susceptor) to activate dopant atoms and to repair damage that was caused by ion implantation. Sheet resistance and Hall effect measurements were used to assess the extent of dopant activation. Rutherford backscattering spectrometry (RBS) with ion channeling was conducted to determine the extent of recrystallization. The dopant activation and recrystallization resulting from microwave annealing is compared with that resulting from conventional rapid thermal annealing (RTA) with the same heating profile. The results show that when compared to RTA, susceptor-assisted microwave annealing results in better dopant activation for shorter anneal times under the same heating conditions.

Jan 1, 2015

By A. F. Saavedra, N. E. Richards, C. J. McMinn

"The aluminum industry in general and Reynolds Metals Company in particular have continued to support development work for improvement of the Hall cell design and for alternative processes for the reduction of alumina. The evolution of the Hall cell design will continue into the next century as a result of further development of mathematical models, sophisticated control systems and new materials for cell components. This paper discusses the areas in which the new generation cell advances will differ from the present day design. Additionally, Reynolds Metal s has supported work for the development of a carbo thermic process to reduce alumina. Theoretical work has indicated that this process could possibly have economic advantage over the Hall process. Several complicated furnace configurations have been proposed to provide the conditions for successfully reducing alumina. The results of small pilot scale operation and most promising furnace design are discussed. For comparison, projected capital investment costs and operation costs are discussed. IntroductionThe evolution of the Hall-Heroult process will continue into the next century. This evolution will be influenced by economics, more .restrictive environment and worker protection requirements, and technological development. These factors will also cause changes in the competitive position of alternate processes for aluminum production.Several aluminum producers have made major investments in alternate processes for aluminum production in the past three decades and there is continued support in some companies for improvements in the Hall-Heroult process and for alternate processes. The more visible development work in reduction technology, not aimed at significant process changes, is in the areas of higher amperage cells with bus bar designs to reduce harmful magnetic effects, more advanced and automated feed, voltage and electrolyte composition control, improved energy efficiency and sol id waste disposal . Efforts to bring significant change to the reduction process are being made in development of materials that can function as inert anodes and cathodes. These materials could lead to the development of reduction cells with multiple bipolar electrodes operating on oxide feed and fluoride electrolytes. Development work on new processes was reduced in the last decade by several companies because of economic and technological realities. Reynolds Metals supported work on a carbothermic process to reduce alumina and produce commercial pure aluminum. This work progressed through small pilot plant operation, and resulted in development of furnace designs and operation regimes. This paper reviews how this and other technologies could influence the reduction of alumina beyond the year 2000."

Jan 1, 1988

By U B. Pal

Downsizing and decommissioning of nuclear facility operations is increasing the stockpile of various different grades of Radioactive Scrap Iron (RSI). Disposal of this material not only represents significant resource and value lost, but also necessitates long term monitoring for environmental compliance. The latter results in additional recurring expense. It is desirable to be able to decontaminate the RSI to a very low level that can be recycled or used for fabrication of containers for RSI disposal instead of using virgin metal to fabricate the container. Electro-Slag Remelting and Refining (ESR) is often used for decontaminating radioactive contaminated sources of scrap iron such as stainless steel. Non-radioactive oxides of cerium are used to simulate the radioactive oxide contaminants of Uranium and Plutonium. The success of the ESR process is strongly dependent on the capacity of the slag to rapidly incorporate the radioactive contaminant (simulant). In this study we have measured the slag-metal partition coefficient for cerium and investigated the reaction mechanism for the dissolution CeO, in the slag.

Jan 1, 2002

By Kenneth N. Pike

The need to comply with environmental regulations and increase production has resulted in modifications to the East Penn blast furnace operation. Changes made include furnace design modifications, closed loop water cooling with heat recovery, automated weighing and charging, automated tuyere punching, ammonia scrubbing of tail gases and improved metal and slag handling to minimize environmental impact. These changes have resulted in a marked increase in yearly production and compliance with many of the air, water and solid waste regulations.

Jan 1, 1990

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 K. Soldenhoff

The Bulong deposit, situated near Kalgoorlie in Western Australia and owned by Resolute Limited, is a lateritic deposit containing on average 1.1% nickel and 0.09% cobalt. A process has been developed and tested at the mini-plant scale for direct solvent extraction and separation of Co and Ni from solutions derived by acid pressure leaching of Bulong ore. In this paper, two solvent extraction processes are described. The first process uses Cyanex 272 to extract cobalt and reject nickel to the raffinate. The second process uses Versatic 10 to extract and purify nickel. The loaded strip nickel solution is suitable for electrowinning. Results of both batch laboratory tests and continuous mini-plant trials are presented. The selectivity of the solvents with respect to the major impurities such as Mn, Mg, Ca, and Zn is also discussed.

Jan 1, 1998

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from the University of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

By Peter K. Liaw, Charlie R. Brooks, David C. Joy, Wei Zhao

In this paper, effects of oxidation, porosity and fiber-fabric stacking sequence on flexural strength of a continuous silicon carbide fiber (SiCr) fabric-reinforced SiC ceramic-matrix composite (CFCC) were studied. The failure mechanisms were correlated with flexural strengths of CFCC samples, both before and after oxidation. Microstructures and fractography were investigated using scanning electron microscopy (SEM). The chemical change after oxidation, such as Si, C, and 0, and their distributions, were detected by the SEM energy-dispersive X-ray spectroscopy (EDXS) line-scan chemical analysis technique. These effects on the strength of the CFCC can be attributed to following reasons: (i) The decrease in the flexural strength after oxidation is mainly due to degradation of the strength of Nicalon fibers and the damage of fiber/matrix interface both caused by high-temperature chemical reactions, (ii) Porosity is not too important in affecting the strength of the CFCC, when the bonding of the forced flow chemical vapor infiltration (FCVI)-SiC matrix is stronger than that of the fiber/matrix interface. However, a higher porosity content will be harmful, because higher porosity will both decrease the effective elastic modulus of the FCVI-SiC and make pore-linkage easier to occur, which is more likely to cause premature failure, (iii) The variation in the lamina stacking sequence of the CFCC changes the elastic stress distributions along the thickness direction of specimens, the magnitude of ceramic matrix-cracking stress, the effective elastic moduli of the laminate, and different crack initiation sites as well as different failure modes, and thus, leading to the scatter in the flexural strength of the CFCC.

Jan 1, 1998

By V. Ramachandran

In view of the increasing environmental regulations that have been promulgated in the last 30 years, non-ferrous smelters and refineries have learnt to handle effectively the process waste streams that need to be bled from the system for impurities' control. The cations of concern are copper, lead, zinc, cadmium, mercury, thallium, nickel, silver, sodium and potassium. Anionic species of arsenic and selenium also need to be addressed, Sulfates and chlorides-not a major concern at present-have come under scrutiny in the recent past. The current paper reviews several treatment options with reference to a) types of waste streams processed b)process chemistry c )discharge options and recovery of treated water and d) sludge disposal. The long term goal of any smelter and/or refinery should be to achieve zero liquid discharge from the plant. Methods to obtain zero discharge are discussed.

Jan 1, 2003

By Manabu lshimaru

Solid-liquid interfaces as well as defect formation processes during crystallization of melted silicon (Si) have been examined by using molecular-dynamics (MD) simulations. The ordinary Langevin equation employing the Tersoff interatomic potential was used for the calculation of the atomic trajectories. A solid-melt interface has a tendency to form {]] I} microfacets during the crystal growth in the [001] direction, while it is essentially flat during the (Ill) crystallization. Because of the difference of the interfacial structures, the structures of grown-in defects and defect evolution depend strongly on the growth direction. We discuss defect structures and their formation processes within the context of our results as well as previous experimental observations.

Jan 1, 2001

By Carl W. Dalrymple

A wide variety of contaminants (heavy metals, suspended solids, colloids, oils, organics) have been successfully removed from wastewater using an electrocoagulation process. An innovative electrocoagulation system is described. This process involves a procedure which subjects dissolved and suspended wastewater contaminants to the simultaneous addition of metal ions in the presence of direct current. During the treatment process Ionic and other charged particles in the wastewater are neutralized with oppositely charged ions generating the coagulation of contaminants: The process Is called CURE, and' presented here with application to wastewaters containing mainly heavy metals.

Jan 1, 1995