Search Documents

By Manuel Alvarado, David Nemir, Jan Beck

"Thermoelectric generation using special N-doped and P-doped semiconductors is well known as a means for direct heat energy to electrical energy conversion without the need for moving parts. The technology is used today in niche markets for low level electricity production and has been proposed as a scalable means for capturing large scale energy from waste heat streams. The choice of geometry of the thermoelements and conductors is critical to the successful implementation of a waste heat recovery system in order to manage losses due to Joule heating and diffusive heat flows. This paper describes a simulation study to define the performance impact of different aspect ratios for the active thermoelements and the electrical interconnect. The use of a finite element model that incorporates the intercoupled heat and electrical energy flows highlights some of the issues impacting scalability.IntroductionThermoelectric phenomena arise out of the intercoupled electrical and thermal currents in a material. A two-element thermoelectric generator is depicted in Figure 1. It is constructed by connecting an N-type thermoelement and a P-type thermoelement in electrical series, with both elements in thermal parallel between a heat source and a heat sink. The electrical series connection is made by attaching conductors as shown. Ideally, these series connection elements will be both good thermal conductors and good electrical conductors.The two element generator in Figure 1 is disposed between two thermal reservoirs: the heat source, which furnishes heat energy; and the heat sink, which absorbs heat energy. Heat energy flux Q, flows from the heat source to the heat sink, driven by the temperature difference between the source and the sink. As depicted in Figure 1, when a resistive load, R, is attached, electrical current, I, may be extracted from the thermoelectric generator and furnished to the load. The N-type and P-type thermoelements, are the active portions that do the actual conversion of heat energy to electrical energy. Although thermoelements may be built using conductors such as bismuth and antimony, higher efficiency thermoelectrics are built using heavily doped semiconductors. Thermoelectric devices are generally formed by connecting many pairs (couples) of N and P type thermoelements in electrical series and in thermal parallel. A commercially available module having 127 couples (254 elements) is shown in Figure 2."

Jan 1, 2011

By A. A. Hejja

The first part of this study deals with the importance of surface tension of slags produced in the smelting of sulphide concentrates. Theoretically the method of determining the surface tension of slags was laid down by Boni and Derge. The values obtained experimentally for a series of main oxide components were grouped into a useful correlation incorporating experimental constants for the relevant oxides present in the slag, some of these giving the surface tension value for the particular slag. These estimated values were coupled with or incorporated into the slag viscosity plots to show the correlation between the two factors. This is also important from a refractory attack point of view in the furnace operation. In the second part an attempt is made toward the optimisation of slag composition relevant for electric furnace smelting processes. Using the knowledge of the viscosity and electrical conductivity of the slags at the temperature of furnace operation, the mode of optimisation is based on correlations which utilize the trend of the mostly parabolic plots of viscosities and conductivities. The results obtained by this method agree well with the optimum slag compositions being used in established operations derived from years of practical experience for various slags used in the furnaces. However, due to extensive turbulence in suspension and gas injected bath smelting processes, the outlined methods cannot be used for these processes. Also great caution should be exercised in their application for three electrode circular furnaces with separate slag cleaning.

Jan 1, 1997

By Greg Dowling, Jun Ge, George Shannon, Shufeng Yang, Yongfeng Chen, Lifeng Zhang

"Inclusions in 316L stainless steel ingots poured using two different upgate designs – a traditional upgate and a swirl upgate - were investigated using SEM and ASPEX automated inclusion analysis. The main inclusions were high SiO2 inclusions, MnS inclusions and SiO2-Al2O3-CaO inclusions. More inclusions were detected at the top of the ingot than other places in vertical direction, and more inclusions were at the edge of the ingot than other place in the radial direction. With swirling upgate there were more K- and Na- bearing inclusions than that with the traditional upgate indicating possible more serious flux entrainment with the swirl upgate.IntroductionIngot casting still is very important for production of special steel grades including high carbon chromium bearing steel, thick plate, seamless tube, forgings, bars, and wire rods [1] . During the bottom teeming process, molten steel enters the trumpet and passes through the spider into the runners. Molten steel then enters the ingot mold through an upgate near the end of the runner. In the early stages of filling a mold, a mold flux bag hung in the mold were burnt and the mold flux will cover the top of the rising steel to protect the steel from being reoxidized, acting as well as act as a thermal insulator. So far, some efforts on studying inclusions characteristics in the ingot have been reported. A review paper on the control of inclusions during steel ingot casting was published by Zhang et al. [2] Zhang also studied Inclusions in bottom-teemed ingots of plain carbon steel and found that the >20µm inclusions originated from either the entrainment of mold flux of the reoxidation during teeming process. [3] The results of Nagendra and Du showed that there were more inclusions in the centre part of the ingot [4]. Eriksson et al reported that the composition of inclusions was more complex in the mold samples in comparison to the ladle samples, and more inclusions in the mold were found than in ladle because of the reaction between the mold flux and the molten steel [5]. It was reported that SiO2-CaO-Al2O3 inclusions originating from mold powder with reoxidation product Al2O3 as a part, and there were more inclusions close to the side wall than the center of the ingot in the radial direction. [6]. A more recent investigation showed that four main types of inclusions in runner samples were classified: oxides, sulfides, complex and carbon-nitrides. [7] The flow pattern in the mold during filling has been found to be an important factor regarding inclusions in the ingot. In the early stages offilling a mold, steel enters the mold through the entry nozzle at a high velocity. The effect of the resulting turbulence on the meniscus can lead to the entrainment of mold flux. Efforts have been paid over the years to find methods to reduce the velocity of the molten steel entering the mold, such as using opening angle of the inlet nozzle [8], using swirl blade at the runner [9], using a divergent nozzle combined with a swirling flow generated in the nozzle [10-11]."

Jan 1, 2012

By Takeo Fujino, Nobuaki Sato, Yarong Wang, Kohta Yamada

"Ternary mixed sulfides of some transition metals MTS3 (M=Ba, ·Pb, T=Ti, Zr) were synthesized by a relatively low temperature process using sulfur melt. The mixture of starting materials, such as, metals and/or binary sulfides and a large excess of sulfur was reacted in a vacuum-sealed Pyrex or quartz ampoule at 350- 600 °C for one to three weeks. After the reaction, the remaining sulfur was completely removed by a process composed of filtration of sulfur melt and followed dissolution in CS2• The binary sulfides impurities coexisted in the products were removed by rinsing the products in water and acetone. By using the above method, BaTiS3, PbTiS3 and BaZrS3 'Were obtained in pure form. The effect of addition of halides on the yields of these ternary sulfides were also discussed.IntroductionThere have been a vast number of studies on the preparation and physical and /or chemical properties of mixed metal oxides. As is well known, some of such compounds exhibit excellent materials properties, causing them for use in mechanical, electronic, magnetic and chemical devices. Not a few mixed metal sulfides show similar physico-chemical properties to those of the corresponding mixed metal oxides. However, the study of the mixed sulfide crystals is rather sparse mainly due to difficulties in preparing these compounds. In various methods which have been adopted for preparing mixed sulfides, the simplest method would be the solid-solid reaction of the component binary sulfides or elements. However, there are always diffusional constraints with regard to the reactions in solid phases causing it necessary to heat the reactants at sufficiently high temperatures, viz. 800-1200°C. On the other hand, some mixed sulfides are unstable at high temperatures or to change their materials properties due to sulfur nonstoichiometry and structural modification depending on temperature, i.e., synthesis of such compounds needs to be made at lower temperatures. Processing in alkali halide melts is hopeful to overcome the above problems but to obtain the halide melts the temperatures above ~ 600 °C is needed. Low temperature reaction has been carried out for the preparation of Hg1.24TiS4, which was formed by the ·combination of TiS2 and molten Hg metal at 320°C[l]. Reaction of WS2 with LiBH4 melt at 350°C yielded LixWS2[2]. These sophisticated methods, however, can be applied only to the vary special cases."

Jan 1, 2000

By Rush Kramer

A bulk compositional chemical analysis often provides incomplete information to help the mineral processor when faced with the problem of removing troublesome contaminants in low concentrations. Michigan Tech has developed a unique approach for addressing this problem. A combination of Scanning Electron Microscopy (SEM). Energy Dispersive Spectroscopy (EDS). and image analysis was successfully used to characterize the species responsible for phosphorus contamination of less than .05 weight percent in iron ore. An automated routine acquired the chemical signature of each particle on a backscattered electron image. The few particles containing phosphorus were identified from the hundreds of particles examined. and the phosphate phases present were easily characterized.

Jan 1, 1991

By I. A. H. Schneiderl

Eichhornia crassipes approaches being a scourge in many parts of the world, .choking waterways and hindering transport upon them. At the same time it is known to readily abstract heavy metal ions from water and, thus, aids in the removal of heavy metals found in such waters. This paper considers the possibility of using specific parts of the plant as an inexpensive adsorbent for the removal of heavy metals from contaminated chemical and mining industry waste waters. In particular the root of the plant was found to be an excellent accumulator of 'heavy metal ions including uranium from solution. It is. also suggested that dried roots of the plant ?might be placed in simple bags and used in a very low cost metal ion removal system.

Jan 1, 1995

By Federico Chavez

The process for recovering lead from battery residues used in several Mexican Plants include lead blast furnace and rotary furnaces. The formers are basically fed with recycled batteries together with the necessary additives to produce metallic lead. One of the by-products generated in the blast furnace is a dust mainly formed by lead sulfide. The rotary furnace is used to recover lead .from lead batteries, dross from the refining-alloying process and the leady fines produced in the blast furnace. This paper describes thennodynamic analysis made to the rotary furnace process to understand the effect that each component of the system has upon the lead recovery. In order to enhance the process, the influence of iron chips composition and excess coke on slag viscosity is discussed. A computer optimization program . has been developed to design the furnace charge based on material and energy balances, .together with the thennodynamic equilibrium calculation.

Jan 1, 1995

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Filiz Sahin

This paper presents a synthesis of TiB2 via carbothermal reduction method using a mixture of TiO2, B4C and C prepared in molar ratio of 2:1:3. Reduction experiments were carried out in a high temperature graphite furnace in a graphite crucible under argon atmosphere at different time (0, 15, 30 and 60 min.) and temperatures (1400, 1500 and 1600 °C). The products obtained were investigated using XRD technique.

Jan 1, 2008

By B. Erik Ydstie, Tor Lindstad, Vianey Garcia-Osorio

"As a result of the high temperatures present in a Carbothermic Aluminum Process the content of aluminum and aluminum sub-oxide in the gases leaving this process is high. These gases as well as energy must be recovered. In a Vapor Recovery Unit were the aluminum compounds react in a series of Heterogeneous Non-catalytic Reactions forming solid, liquid and gas products. The different product phases depend on the temperature present in the system. In this work we present dynamic model of the Vapor Recovery Unit of a conceptual Carbothermic Aluminum Process. Because of the complexity of the system several models are developed and coupled to capture the essential physics of the multiphase reaction problem. A Shrinking Core Model describes the reaction mechanisms. Then material and energy balances are coupled with the thermodynamics properties from the FACT database of thermodynamic properties, resulting in a system of nonlinear Partial Differential Equations. In the paper we describe the model development and governing equations for the reaction mechanisms and fluid flow. Finally we review the numerical schemes created for the solution of the model system. The model can be used for control and design purposes.IntroductionThe Carbothennic Processes for producing Aluminum can be divided into two groups (Motzfeldt et al. (1989)) In the first approach pure alumina is produced and reduced to pure aluminum. In the second approach an alloy (e.g. aluminum and silicon) is made and then aluminum is produced from the alloy. The history of both processes has been described by Ginsberg et al. (1965). At least three aluminum producers began largescale testing of this process in the 60's Alcan, Pechey-Ugine and Reynolds. Alcoa did some smaller scale experiments.Alcoa was one of the first companies to produce aluminum by Carbothennic Reduction (Foster et al. (1956)) and US Patent 2,829,961 April 8, 1958. In this process a carbon containing molten aluminum phase was a floated on top of an oxy-carbide melt. During the cooling the dissolved carbon deposited as aluminum carbide. The carbide was then separated from the molten aluminum by a fluxing agent. This process was successful but economic unfeasible."

Jan 1, 2001

By Darryl Lovato, Ramiro Pereyra, Daniel S. Schwartz

"During an annual inventory of nuclear material, a plated steel container which contained plutonium oxide failed. The container had been packaged for temporary storage but had been overlooked and remained in storage for more than 23 years. Although it was determined that the failure occurred through the slip-top rim, a metallurgical evaluation was requested to help to determine the integrity of the container.Optical metallography and scanning electron microscopy were used to analyze the character and degree of corrosion in the container. The depth of corrosion, measured at approximately 10 µm, did not pose a threat to the integrity of the container. However, the corrosion morphology and chemistry did suggest that a galvanic cell had developed between the tin and steel from the condensation of water. The morphology also suggests that the attack of the steel took place over a series of cycles due to changes of the environment.IntroductionMetallographic analysis was requested as part of the investigation into the mechanism of the failure of a slip-top container (#38621) containing plutonium oxide (PuO2) powder. The container had leaked during a special nuclear material (SNM) annual inventory causing contamination and closure of the vault. A photograph of the container and interior container is shown on the right in Figure 1. An initial investigation established that the source of contamination was the consequence of the failure of multiple layers of containment. Initially by the deterioration of the interior plastic bottle and polyvinyl chloride (PVC) bagout bag, and finally through the lid and steel container interface at a location where tape had not adhered properly [1]. Although the source of the breach was established, it was determined that metallographic analysis was important to establish the extent of deterioration of the steel container."

Jan 1, 2008

By Joseph Sofra

It has become increasingly evident that sustainable metals production in the 21st century requires producers to balance the needs of cost effective, high value production with that of responsible plant operation. This is becoming more difficult as lower grade and more complex feed materials, including recycled scrap and residues, are being processed to reduce production costs and decrease exposure to primary metal market fluctuations. One particular facet of the metals industry facing these challenges in the 21st century are copper producers, The recent steady decline in the copper price has seen the industry cut expenditure, tighten control on income streams and focus on high returns on capital investment. For these reasons copper producers are looking towards flexible technologies that can deliver high value products, with minimal environmental impact at low capital and low sustainable operating costs. Ausmelt's Top Submerged Lancing (TSL) technology for copper production is a low cost, proven technology for the processing of both primary and secondary copper materials. Both the smelting and converting operations introduce significant advantages in environmental performance, improved process efficiencies and high rates of metal recovery, Ausmelt has made significant gains in the past 4 years in establishing a strong market position for its copper technology, New installations in China, South Africa and India as well as existing operations in Zimbabwe and China have demonstrated its effectiveness. This paper reviews the application of Ausmelt Technology for both smelting and converting of primary and secondary sources, It discusses Ausmelt's design and implementation philosophy, and how this philosophy meshes with the needs of the end user.

Jan 1, 2003

By Larry B. Fiske

Elimination of dust and processing of fines for both thermal and metallurgical coals is addressed. The efficiency of treatment with lignosulfonates compares favorably to oil in thermal coal. Effect of treatment with various lignosulfonates upon cokability of metallurgical coal was determined by Free Swelling Index, Gieseler Plasticity and Arnu Dilatation.

Jan 1, 1992

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Sang Han Son

The vapor pressures of FeCI2 and ZnC12 in the FeCl2-ZnCl2 system were measured by the transpiration method at 873K and 917K. The vapor pressure data were interpreted to indicate the formation of complex ions in the FeCl2-ZnCl2 melts. It is presumed that the complex molecule FeZnCl4 as well as FeCI2 and ZnCI2 exists in the vapors in equilibrium with molten FeCl2-ZnCl2 mixtures. The activities in the FeCl2-ZnCI2 system are shown a negative deviation from Raoult's law. These results suggest the formation of complex ions such as ZnCl42- in molten FeCI2-ZnCI2 mixtures.

Jan 1, 2003

By Francis Vanbellen

Umicore Precious Metals Refining operates an integrated precious metals smelting and refining plant in Hoboken, Belgium. Once a smelter and refiner of complex concentrates, the plant today?s feed consists exclusively of industrial and consumer recycled products, making it the world?s largest recycling facility for precious metals. Unlike the fairy tale of the Frog Prince, it took much more than a princess? kiss to successfully realize this makeover. A completely renewed plant has been built over the past decade. The most visible technological innovation was the commissioning of the Pb-Cu smelter. Its flexibility towards very different types of feed makes it perfectly suited as main entry to the Hoboken flow sheet. A new Cu-leaching & electro winning plant and precious metals refinery make up the Precious Metals Operations (PMO) whose targets are fast throughput and maximized yields for gold, silver and the platinum group metals. The Base Metals Operations (BMO), flexibly process the by-products from the PMO, valorizing ?impurities? like indium, tellurium, selenium and others. Off gas and waste water treatments ensure compliance with strict environmental standards. Precious metals recycling is an art that goes beyond mastering a unique flow sheet. Umicore Precious Metals Refining offers a complete recycling service, taking care of sampling and assaying, metals management and logistics. The quality of this integral service is recognized through the attribution of ISO certifications for our operational activities, sampling and the environmental care. And it?s an art that follows Michelangelo?s experience: ?Art is 5% of inspiration and 95% of transpiration.?

Jan 1, 2006

By Melvin A. Jennings

Ion-exchange technology for precious metals recovery is at a turning point. Some very exciting technology has been developed in the past five years which should lead to commercialization of the process. Ion-exchange will allow not only for the recovery of gold and silver, but also will allow for the recovery of cyanide form plant tailings. This process may soon be competitive with Merrill-Crowe for silver and once this occurs, it will become the process of choice.

Jan 1, 1991

By Thomas Brynjulfsen, Merete Tangstad, Eli Ringdalen

Manganese ore fines cannot be added to the submerged arc furnace directly as they will prevent even gas flow through the burden. Low gas permeability in the burden will lower the degree of pre-reduction of ore subsequently increase the carbon and energy consumption of the process. In order to utilize manganese ore fines in the furnace, they are typically agglomerated into sinter. In this work, the melting and reduction properties of Gabonese sinter and Gabonese ore have been investigated in pilot scale experiments. Two experiments were conducted, one with 100% sinter as manganese source and one with 50/50 sinter and ore. Lime was used to achieve a charge basicity of 0.72 in both experiments. The composition of slag samples from the excavation of the furnace was established using EPMA(WDS), and the composition of the tapped slag and metal was found using XRF. It was found that while the coke-bed size would determine the tapped slag composition, the melting behavior of the Mn source would determine the mixing with lime.

Jan 1, 2014

By Ryokichi Shimpo, Akio Fuwa

"The process-measurements of copper smelters in Japan were investigated for the summary of the latest technique and for the fundamental study of process control. The smelters investigated are those employing flash smelting furnace and P.S. converter, one reverberatory furnace and P.S. converter, and one continuous smelting converting furnace (M.I. process). Respective process is then considered, consisted of several reactors of different functions. The measurement methods were summarized in each reactor, including the measurement points. The methods of chemical analyses of the samples in each reactor were also investigated.IntroductionAn investigation on the process measurements, chemical analyses, and system control in copper smelters in Japan were carried out for understanding and summarizing the technique of the pyrometallurgical copper smelting operations. The typical seven processes in six copper smelters were investigated in the period from 1985 to 1987. The smelters investigated were Touyo Smelter of Sumitomo Metal Mining Co., Ltd., Kosaka Smelter of Dowa Mining Co., Ltd., Saganoseki Smelter of Nippon Mining Co., Ltd., Tamano Smelter of Hibi Kyodo Smelting Co., Ltd., Ashio Smelter of Furukawa Co., Ltd. and Naoshima Smelter of Mitsubishi Metal Co., Ltd. They include five flash smelting furnace and P.S. converter systems, one Mitsubishi continuous smelting and converting process (M.I. process), and one reverberatory furnace and P.S. converter system.The investigation was performed by making inquiries about the measurements, chemical analyses, system control, and their future prospects to the engineers in each smelter and by summarizing up in each item. The system control and future prospects were summarized in another paper titled ""Process Control Scheme of Copper Smelting Processes in Japan and Future View."

Jan 1, 1989

The present work is mainly focused on developing intermetallic inert anodes for aluminum electrolysis. The anode alloy based on Al-Ti-Cu system was prepared by casting, followed by the application of a protective coating. Behaviour of corrosion and the passivation under anodic condition was characterized using the electrochemical and microscopic techniques. The results obtained clearly demonstrate that the oxide coating can provide good corrosion resistance via surface passivation of alloy anodes, rendering them inert in cryolite melt.

Jan 1, 2006