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By Robert W. Bartlett, Keith A. Prisbrey

"Natural biooxidation of shallow, refractory ore heaps, relying on gaseous oxygen diffusion from the heap surface is attractive because of its simplicity and potential low cost, especially without using a lined pad, which is possible if percolation of leachate through the heap is avoided. In this case, the excess oxidation enthalpy must be removed by water evaporation from within the wet ore heap, and the rising water vapor flux within it will impede the downward oxygen flux. An analysis of this process shows that for typical values of pyrite grades and limited temperature increases in the ore heap, the oxidation rate and penetration into the heap is reduced to values between about 30 percent and 50 percent of those obtained when leachate percolation occurs and water evaporation is not a significant mechanism of heat removal.IntroductionHeap biooxidation of refractory gold ores, needed as a pretreatment step to liberate the gold for subsequent extraction by leaching, requires large amounts of oxygen for the normal amounts of sulfide minerals that are typically present, one to two percent pyrite and/or arsenopyrite.The importance and potential limitations of oxygen transport into commercial ore heaps, which are much larger than encountered with column tests of ore and with pilot heaps, has been recognized111 • Commercial ore heaps using radial stacking conveyors are typically about nine meters high and may be 100 meters or more in lateral dimension. Three oxygen transport mechanisms have been identified and analyzed: ( 1) natural convection, which arises from an increase in buoyancy caused by the temperature rise and gas composition changes associated with the exothermic oxidation of the sulfide minerals within the ore heap, (2) forced air ventilation, using low pressure fans and air distribution pipes within the heap, and (3) diffusion of oxygen in the gas-filled void spaces within the ore heap driven by the oxygen concentration gradient from the surface of the heap to the mineral oxidation loci within it."

Jan 1, 1997

By Nobuaki Sato

For decontamination of SO2 containing waste gases from industries such as ferrous and non-ferrous metal companies, desulfurization with hydrogen production by the reaction of Br2 and SO2 was proposed as bromine-sulfur (BS) process. In this process, SO2 is fixed as H2SO4 in the presence of Br2 and H2O forming H2SO4 and HBr. Then hydrogen is produced by the decomposition of HBr and Br2 as byproduct is recycled. The reaction of Br2, SO2 and H2O was found not to occur in liquid phase but to occur in vapor one. The production ratios of H2SO4 and HBr showed a maximum at temperatures around 60 oC. The highest production ratio was obtained at 70 oC with a mixing ratio of Br2:SO2:H2O=1:1:10. The experimental results were discussed with thermodynamic consideration.

Jan 1, 2006

By Gil Bourcier

A process has been developed for detoxifying spent potliner (SPL) in which the SPL is blended with limestone and an anti-agglomeration agent and thermally treated in a rotary kiln. The process has been proven and a commercial plant is in operation at Gum Springs, Arkansas. The treated by-product material has been delisted by the U.S. EPA and is now a potential raw material for many commercial applications. Finding uses for a non-hazardous material has many advantages over finding uses for a hazardous material like SPL. Complete usage of the by-product will complete the life cycle and eliminate any landfilling of non-hazardous SPL by-products or residues. Being non-hazardous and containing compounds used in the ceramic and numerous other industries assures many potential uses for the spent potliner by-product.

Jan 1, 1994

By Gabriel Riveros

Fire refining of copper consists of two stages copper oxidation and copper reduction. Very frequently the capacity of the anode furnace is determined by the rate of copper reduction. The analysis of factors affecting the rate of the oxygen reduction from a liquid copper with solid carbon or injected hydrocarbons pointed out the role of the mass transfer in a liquid copper in final stage of the reduction. Experimental results of copper reduction with graphite and injected natural gas in laboratory- scale crucibles showed two stages of the reduction process with a sharp change of the controlling mechanism. The estimated dynamic surface area of gas bubbles based on the measured bubble frequency and the gas flowrate allowed for the detennination of the reaction constant as a degree of the partial pre-combustion of the air/natural gas mix. The variation of the used reductant as a function of the oxygen concentration and temperature has been evaluated based on the detennined kinetic model. The intensification of copper reduction in fire refining has been discusses on the basis of obtained kinetic data and analysis of various factors detennining the time of reduction.

Jan 1, 2003

By Brandon R. Ball

An investigation of the effects of ozone and ozone-induced hydroxyl radical on reducing whole effluent toxicity is described and discussed relative to the application of ozone for industrial water treatment. Results from operation of an ozone system treating industrial effluent from a lead and zinc mine in Colorado are presented. The mine discharges 1,000 gpm of wastewater into a tributary of the Arkansas River and has historically exceeded Whole Effluent Toxicity (WET) limits and on occasion has exceeded numeric limits for copper, ammonia, and cyanide. Based on results of a Toxicity Identification Evaluation (TIE) conducted on the effluent and individual process waste streams, the source of effluent toxicity is believed to be primarily associated with organic reagents used in the milling process. Based on test results, an applied ozone to COD ratio of 3: 1 by weight and a contact time of 30 minutes was found to be effective for reducing whole effluent toxicity at pH 11 but not at pH 7, indicating oxidation by hydroxyl radical to be the dominant mechanism responsible for toxic-ity reduction. At an applied ozone to COD ratio of 3:1 and a pH of 11, toxicity was improved from 0 percent survival to 100 percent survival for Ceriodaphnia dubia and fathead minnow (Pimephales promelas) based

Jan 1, 1996

By Behrouz Abedian, Livia M. Racz

"We address dynamic interactions between high-energy, reactive surfaces of polymer-matrix composites and solid surfaces. A common characteristic of these interfaces is that bonding occurs readily upon contact. In many industrial and biomedical applications, it is desirable to suppress this bonding phenomenon. This interfacial effect is discussed in light of the development of our new method of handling polymer-matrix composites in dental applications. This method involves vibration of the solid-polymer interface at different frequencies. For each material, there is a critical frequency at which the sum of the viscoelastic and inertial energies of the fluid at the surface exceeds the energy available for bonding. When the polymer is vibrated at or beyond this frequency, it does not adhere to solid surfaces. An important aspect of the developed process is that it can be used to characterize surface and interfacial properties of polymers under dynamic conditions, whereas existing techniques are restricted to the study of bulk dynamic properties.IntroductionThe purpose of this paper is to report on the development of a new method for manipulating polymer-matrix composite materials used in dental applications, and the potential of this process for use in materials characterization. The materials under discussion have polymer matrices of a combination of bisphenol A-glycidyl methacrylate (BIS-GMA) and triethylene glycol dimethacrylate (TEGDMA), and contain filler particles of silica and/or zirconia glasses. These materials are called direct aesthetic restorative materials, and are used for filling of cavities, repairing chipped teeth, and for other restorations in which appearance is of importance. They have the appearance of natural tooth material, and are therefore in great demand for use in the anterior portion of the mouth(l,2)."

Jan 1, 1998

By J. B. Cocanour

Pioneering work at the U.S. Bureau of Mines (USBM) has produced a personal computer (PC)-based, software-driven video photometric color sensor for real time process control of metallurgical streams. The video photometer is an inexpensive optical sensor which operates in the visual area of the electromagnetic spectrum and collects color information through plastic optical fiber. The red, green, and blue (R/G/B) voltage components of the color video signal are digitized and characterized through software and then presented as the control variable for software-based proportional-integral-differential (PID) control. This sensor has been successfully employed in the control of a laboratory copper electrolytic circuit. With this sensor, copper solutions were analyzed on-line without the need for sample removal, dilution, mixing or reagent addition, thereby allowing for the real time control of the circuit.

Jan 1, 1994

By Hideki Yamamoto

A new technology to convert fluoride gas (C2H2F4 : R-134a) contained in the exhaust gases from semiconductor manufacturing plants and refrigerators directly into a harmless substance have been established, thus, presenting a new concept for the disposal of fluoride gases such as CFCs that are associated with the global warming. Experimental results verify that chemical reactions with metal compounds can take place at substantially lower temperatures of 700- 800K as compared with combustion treatment temperatures of 1200-1500K. The reaction product is mainly metal fluoride, which chemically is a harmless material. Furthermore, this process is compact, easily controlled, safe and has low running costs. This paper deals with a new chemical reaction method for the harmless disposal of gases effecting the global warming.

Jan 1, 2003

By Nils Eivind Kamfjord, Mari K. Næss, Gabriella M. Tranell

"In oxidative ladle refining (OLR) of silicon, the metal surface is oxidized resulting in the formation of a condensed silica fume (SiO2). In the current work, industrial measurement campaigns were performed aiming to measure the fume generation during OLR. A thorough discussion of the possible mechanisms has been included in order to improve our understanding of the Si(1)-O2(g) system.The measurement campaigns were performed at the Elkem Salten plant in Norway. In addition to fume generation from OLR, the metal temperatures and ladle purge gas amount were recorded. The results of this work suggest that fume generation during OLR results from splashing of the metal and/or oxidation of the metal surface, with oxygen transport to the metal surface being the limiting factor. Other mechanisms of SiO2 formation were investigated, however insignificant.IntroductionOne of the main environmental and economical challenges facing the metallurgical industry is fugitive emissions of both materials and energy. In the production of metallurgical grade silicon (MG-Si), refining of the silicon generally takes place through an oxidative ladle treatment (purging with an air-O2 mixture). In the refining process, exposure of silicon to air results in the formation of condensed silica fumes (SiO2) – one of the main sources of fugitive emissions in silicon production plants. The oxidation of liquid silicon, as opposed to solid silicon, has not been widely studied and described in the literature [1], thus a thorough investigation of the oxidation mechanisms, and factors affecting the oxidation reaction rate are essential in order to deal with the problem. In the current work, the rate of liquid silicon oxidation has been studied through industrial measurements of fume generation from refining adles, where the purge gas rate and composition have been varied. The results from these measurements were discussed in light of existing models describing the liquid silicon oxidation kinetics."

Jan 1, 2011

By Ken-ichiro Uemura

"The DIOS process has been developed for eight years since 1988. The research project was started with the element studies carried out by each of the five integrated steel making companies in Japan, the final two and half years were spent for the pilot plant studies. Operation were conducted in the entirely closed and pressurized system successfully as planned. From the result, the DIOS process was proved to be viable as a future iron-making process substitutable for the conventional blast furnace. In addition, a lot of findings were obtained. Hot metal productivity was primarily determined by a oxygen flow rate, and a coal consumption varied depending on the productivity. The post combustion ratio was a little lower than expected from the result of the element study. It was supposed to relate the gas-reforming with coal or volatile matter in the free space of the furnace. Hot metal carbon content seemed to depend on the char content in slag.INTRODUCTIONThe JISF's DIOS pilot plant (DIOS=Direct Iron Ore Smelting Reduction Process) has finished its last campaign of the operations in January 1996. The project was started in 1988 as a joint research of the Center for Coal Utilization, Japan and the Japan Iron and Steel Federation (JISF) with a subsidy for promoting coal productions and utilization technologies from the Agency of National Resources and Energy, the Ministry of International Trade and Industry(MITI). Throughout the pilot plant test, a total of over 20,000 tons of hot metal was produced for more than 2,000 hours of the operation. Recorded production rate was 538 ton/day for 3 days at a specific coal consumption of approx. 1,000kg/hmt. Long-term operation was carried out in the fifth campaign for 18 days, which has proved that the entirely closed and pressurized DIOS process works well as planned. In Figure 1 is shown the representative operational performance obtained in the first five campaigns. The project is going to be finished by the end of March this year after investigating the technical viability and economic potential of the process, and completing the conceptual design of the DIOS commercial plant. In this paper, the system and facilities of the DIOS process are first introduced and some of the results of the pilot plant test are detailed later."

Jan 1, 1996

By Takashi Miyamoto, Hideo Nakae, Hideki Yamaura, Takeshi Yanagihara

"For the production of partially composed metal matrix composites, namely discontinuous MMCs, using a casting· process, the interpenetrated phase composites with SiC particles were fabricated by pressureless iDfiltration using molten Al-Si alloys. This process is based on a wetting phenomenon, therefore, we discussed the technique based on the reactive wetting. The SiC particles coated by diluted water glass were sintered in a mullite Tammann tube and simultaneously infiltrated with molten Al-Si alloys in air at 1173~1573K. As for the improvement of the wettability between the SiC and the liquid aluminum alloy, Fe3O 4 powder was mixed with the water glass due to the thermit reaction between Fe3O4 and molten aluminum alloy. In some experiments, pure aluminum powder was placed on the sintered SiC to increase the interfacial area and the chemical reaction between the sintered Sic. and the melt. By combining these conditions, we succeeded in the complete infiltration without pressure at 1173K.IntroductionAs is well known, the mechanical properties of metal matrix composites (abbreviated MMCs) are superior than that of ordinary metals. However, their use has not been widely accepted because the production cost is very high due to their poor machinability. Therefore, the production of partially composed, namely discontinuous MMCs, by as the Lanxide process [l,2] has been investigated for many years. The Lanxide process, it takes a long time, sometimes up to 10h, in a nitrogen atmosphere for the infiltration. Therefore, the cost will be higher for common use. On the other hand, a high 'pressure process has been adopted for the production of discontinuous MMCs by the Toyota Motor Corp.[3]."

Jan 1, 2000

By Huanmei Yuan, Yuanyuan Wang, Hao Bai

Composite phase change materials are widely used in energy-saving and energy efficient process. Nano-encapsulated phase change materials are especially significant for making advanced working fluid applicable to waste heat recovery or storage. In this study, silica-coated stearic acid (SA) Nano composite phase change materials were prepared from tetraethyl orthosilicate (TEOS) and stearic acid (SA) via sol-gel process. The materials were investigated by Field emission scanning electron microscopy (FE-SEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy(FT-IR) and Differential scanning calorimeter (DSC).The FE-SEM and TEM results show that monodisperse microspheres with stable core– shell structure were formed and SA was encapsulated in the silicon dioxide shell. The FT-IR results show that there were no chemical reaction between silicon dioxide and SA, which is the chemical property of the composite material, is stable. The DSC results show that the composite phase change material has favorable heat capacity.

Jan 1, 2016

By N. A. McKay, J. G. Davison

"Heap leachable ore deposits from many countries have been submitted for process mineralogical evaluation and laboratory testwork. Numerous factors must be addressed and integrated by the mineralogist, geologist, metallurgist and engineer. Projects encompass grass roots exploration, preliminary petrographic analysis, predictive and process mineralogy, dye penetration analysis of rocks and thin sections, metallurgical beneficiation testwork and plant optimization studies. The significance of mineralogical factors, such as geological controls, degree of oxidation, dye amenability, liberation, deleterious minerals, refractoriness, and the impact of mineralogy on gold recovery and process considerations, will be presented.ABSTRACT ONLY"

Jan 1, 1997

By Zenjiro Asaki

The copper concentrate particles dissolve quickly into the molten matte in the smelting furnace of Mitsubishi Process, which indicates that the sulfide smelting is essentially a gas/liquid reaction. In this paper, theoretical calculation has been made on the rate of oxidation of FeS component in the matte to form FeO by rising gas bubbles using the penetration theory. The results showed that all the oxygen in the bubble of 1.2 cm in diameter, which is the maximum stable diameter, is consumed in 3 ms. This time required is sufficiently short, and it results in the actual operation of smelting furnace of 1100% oxygen-efficiency. These calculations indicate that most smelting reactions are completed just under the lance, except slag formation.

Jan 1, 2002

By Robert E. (Bob) Brown

Magnesium was discovered by Davy in 1808. The production processes as they exist are not economically competitive with aluminum The electrolytic magnesium process is divided into two steps; one to make the MgCh feed and the other to apply large amounts of electric current to dissociate the feed into magnesium (450 g) and chlorine (1200 g). The production of fuJIy anhydrous, pure cell feed is a major problem Recently, there has been a growth of thermal processes, mainly the Pidgeon silicothermic production process using FeSi to reduce dolomite in horizontal retorts. Pechiney has a large vertical electrical furnace process that also uses FeSi to reduce calcined dolomite in a molten bath containing alumina. Work is proceeding to develop new or modified processes that will greatly improve magnesium production. The present methods and the research and R&D will be reviewed in this paper.

Jan 1, 2001

By A. G. Raraz

Reactive metal electrorefining presents a number of problems that pose obstacles to commercial operation. Cerium has been chosen as the surrogate for certain reactive metals because of its thermodynamic and electrochemical characteristics. A comparative review of the properties for cerium and plutonium has been presented to justify the choice of cerium as the surrogate metal for studying electrorefining. This review has addressed the electrochemical, thermodynamic, and kinetic parameters of molten salt electrorefining of cerium metal to provide an insight to this extremely important process. The cell components and configuration, current efficiency of the process, purity of the cathodically deposited metal and the power requirement of the system are evaluated for a molten CaCl2-MgCl2 salt electrolyte using a molten, stirred impure anode. Crucible designs, salt electrolyte, cell temperature and electrode materials are also evaluated. Selection of the salt electrolyte and the cell temperature have been suggested from this study.

Jan 1, 1992

By M. T. Ernett

Significant amounts of arsenic are often present in effluents arising from the mining of sulfide ores for the extraction of metals such as copper, gold, lead and zinc. The arsenic is usually removed from the process effluent by co-precipitation with iron because of its common occurence in the mined ore bodies and the excellent adsorptive property of the precipitated hydrous ferric oxide compound. There has been controversy, however, over the long-term stability of the arsenic-bearing ferrihydrite which is produced. This paper presents the results of laboratory studies which indicate that the cations of calcium, magnesium, zinc, cadmium and lead, increase the pH range of effective arsenic adsorption in the Fe-As precipitate from 4-7 to 4-9. The increase in the pH range is similar for all of the added cations investigated. Sulphate ions are shown to have a minimal effect on the residual dissolved arsenate concentration. Silicate ions reduce the adsorptive capacity of ferrihydrite if they are present before the arsenic is adsorbed.

Jan 1, 1994

By T. S. Montgomery

The performance of carbon-magnesia brick in electric arc furnaces (EAF) is interpreted in light of their observed optical microstructures. Features at the bricks' hot faces were protruding periclase grains, metal globules, graphite-metal contacts and linear void patterns. These features were com-pared to similar features previously seen from microstructures of basic oxygen furnace (BOF) refractories. Modes of formation were sought; an attempt was made to interpret their influence related to wear mechanisms.

Jan 1, 1982

By Hani Henein, J. Barry Wiskel

"The easy accessibility and power of the PC, as well as the education of our engineering students in the use of these tools, are compelling reasons for developing computer aided instructional (CAI) tools. There are a wide range of areas in the engineering curriculum where students must learn the steps and the process of applying judgement in problem solving. In the typical course instruction, · an instructor introduces theory to students; the application of the theory to solving problems is often demonstrated in the abstract. Students therefore spend a significant amount of time learning how to apply the theory to problem solving. Additional time and effort must then be spent to get students to the point of learning concepts and integrating this knowledge. A number of computer aided packages have therefore been developed for use in several courses in the materials science and engineering curriculum that encompass both calculational and instructional capabilities. This paper presents an overview of some of these packages which include the solution of a non-linear equation, the instruction of binary diffusion couples, an introduction of crystallography, an introduction to heat transfer and the solution of thermodynamic stability diagrams. The context in which these CAI Tutorials were developed and are being used will be discussed. The pitfalls in the development of these packages will also be discussed. The use of the tutorials has important implications on the expectations from an engineering education of both instructor and student.IntroductionTraditionally, it is quite routine to teach engineering students how to use a computer (the PC today for undergraduates) as a tool in performing engineering calculations or in simulating a process or a unit operation. This often takes the form of one course in computer programming, whether it is Fortran, Visual basic or a spreadsheet, and another course in numerical computation. However, the materials and electronic revolution have brought about considerable advances in computer power and speed, and accessibility. Today, the manipulation of digital images, movies, and speech are commonplace on a desktop PC.' Many mathematical models that were executed only on workstations can now be readily handled on a PC. Concurrently, more of our students own a PC even if their curriculum does not require them to purchase one. Today, virtually every university student has been introduced to the PC in either their elementary or high school education. Hence, the increased capabilities and accessibility of the PC and the familiarity of students with this tool make it compelling to explore its use as an educational tool for our engineering students. This is not a traditional role of a computer in our engineering curriculum."

Jan 1, 2000

"Hematite pellets were electro-deoxidized to iron in molten sodium hydroxide to produce iron containing about 10-wt % oxygen. The anodic reaction was the evolution of oxygen on an inert nickel anode. Before the electrochemical reaction, there is a reaction between sodium hydroxide and ferric oxide to form sodium ferrite and, in order to compensate for the reduction in sodium oxide content, 1 wt % sodium oxide is added to the melt. In a laboratory cell, the cell voltage was 1.7 V with a current density of 5000 A m-2, a current efficiency of 90% and an energy consumption of 2.8 kWh kg-1.Introduction The iron and steel industry contributes about 2.3 bn tonnes/annum of the carbon dioxide to the atmosphere, which is about 10% of the total, and some believe that, in order to prevent a catastrophic rise in the earth’s temperature, carbon dioxide emissions must be reduced by 50% come 2050. However, by 2050, it is likely that the iron and steel industry would have grown significantly so that the production may have risen to 2 or 3 bn tonnes/year so in order to meet the 50 % reduction on today’s figure, the carbon dioxide may have to be reduced to 25% or less, which is a very demanding requirement. There are probably three ways of reducing the carbon dioxide output:1. By capture and sequestration, but this may be technically very demanding.2. Reduction using hydrogen in place of carbon."

Jan 1, 2009