Search Documents

By N. G. Azeredo

This work dealt with the evaluation of engineering structural clay brick samples that were sintered at estimated temperatures of 700 and 800°C. They were collected in a red-brick plant in Campos dos Goytacazes, RJ, Brazil. From a lot, a sample already sintered in its kiln at 700°C were collected and also a sample from the same lot only dried by the air, which were then sintered at 800°C controlled temperature. The samples were subjected to Brazilian Standard tests (ABNT NBR 15270:2005) to determine their geometric, physical and mechanical properties. In order to be classified as structural clay brick it is required minimum 3.0 MPa for the characteristic compressive strength (fbk) to be suitable for up to five floors structural building applications. We also used the Weibull Probability Plot and Weibull Maximum Likelihood Estimation to evaluate distribution parameters in order to compare the results of compressive strength obtained in the tests.

Jan 1, 2015

By D. Lui, B. G. Thomas, B. Ho

"Results from mathematical models and plant experiments are combined to quantify the effect of transverse depressions and oscillation marks on heat transfer in the continuous casting mold. A heat transfer model has been developed to calculate transient heat conduction within the solidifying steel, coupled with the steady-state heat conduction with the continuous casting mold wall. The model features a detailed treatment of the interfacial gap between the shell and mold, including mass and momentum balances on the solid and liquid powder layers. The model predicts the solidified shell thickness down the mold, temperature in the mold and shell, thickness of the resolidified and liquid powder layers, heat flux distribution down the mold, mold water temperature rise, ideal taper of the mold walls, and other related phenomena. The important effect of non-uniform distribution of superheat is incorporated using the results from previous 3-D turbulent fluid flow calculations within the liquid cavity. Results from plant experiments confirm that transverse surface depressions and oscillation marks form at the meniscus and move down the mold. Measurements of mold thermocouple temperatures and breakout shell thickness were used to calibrate the models. The results indicate that the surface depressions and oscillation marks are filled with mold flux, but still have a significant effect on decreasing heat transfer. The predicted mold temperature fluctuations are consistent with measurements. If the depressions become filled with air, their effect is greatly increased. These results should be useful in the difficult task of interpreting transient mold thermocouple signals for on-line quality monitoring.IntroductionMany different types of intermittent surface defects on steel slabs arise during initial solidification in the mold of the. continuous casting machine. These defects include deep oscillation marks, surface depressions, and cracks. They may lead to quality problems, such as slivers, in the final rolled product. In severe cases, breakouts may occur, where liquid steel bursts through a thin section of the shell and drains over the casting machine below the mold."

Jan 1, 1997

By Timothy W. Ellis, John A. Howes, Roger D. Feldman

The new generation of more powerful, energy-intensive devices for communications, industrial production, energy storage and other purposes is creating new challenges to guard against environmental harm and protect national security. Many devices are designed, used and disposed of in a linear, rather than circular manner. This causes scientific, legal and economic issues because the life-cycle costs of components are not adequately considered. Dealing with these issues in isolation from each other can lead to unintended consequences. New models to confront these issues are being defined. This paper suggests a fundamental tool for dealing with material science issues while taking into account the engineering, economic and policy perspectives. That tool is the development of a true, levelized cost of energy storage model with a wide spectrum of inputs for comprehensive analysis. This paper will discuss inputs and the process which can yield meaningful, useful comparisons among batteries and energy-intensive products.

Mar 1, 2018

By E. T. de Groot, D. L. Verhelst

With the successful start-up of Cominco's new KIVCET smelter, the final key component is now in place for Trail Operations to operate efficiently as a modern integrated zinc-lead facility. Unique metallurgical, operational, planning and management issues apply to this operation. Along with presenting the current flowsheet for Trail Operations, this paper discusses issues such as the impact of recycles, operational re-stabilization following significant process changes, plant operation with just-in-time inventories, real-time process optimization, and management philosophy.

Jan 1, 2000

By Kosei Morita, Osamu Nakano, Katsuhiko Nagai, Kazuhiro Mori

"The Sumitomo Toyo Smelter and Refinery commenced its operation in 1971 with three Peirce- Smith (PS) converters. “2 hot – 1 blowing” operation was practiced, that is one of two available converters was blowing and the other was standby in a hot state while the third converter was under repair. After several improvements, the stack time ratio reached around 90%; and processing 5 batches a day became possible.As a result of the expansion program of the Toyo smelter and refinery that started in 2001, the converter operation pattern was shifted from “2 hot – 1 blowing” to “2 hot – 2 blowing” with the installation of second converter blowers and an additional ladle crane.In 2005 a, the fourth converter was installed and “3 hot – 2 blowing” operation began. Also, with improvements experienced in the anode furnaces and the anode-casting wheel operation, today, the number of cycles has been increased up to more than 8.5 a day.The treatment techniques of fugitive gas containing sulfur dioxide from converter furnaces have been gradually reinforced, and the fixation rate of treated sulfur is currently being maintained at more than 99.9%. This paper introduces the operations described above, and the improvements in environmental management techniques for the Toyo PS converter operation."

Jan 1, 2009

By Jasper Kwong

The recycling of MgO-C refractories as a slag conditioner in EAF (electrical arc furnace) foaming slags have been evaluated by the Albany Research Center. The amount of MgO in the slags is critical for the foaming quality. Good foaming slags provide the benefits of high energy efficiency and low refractory consumption and require saturation with MgO. A computer model predicting the chemistry of MgO saturated foaming slags was designed to predict suitable amounts of MgO additives from MgO-C spent refractories. This model can also help to reduce the amount of slags and to improve the economics of producing steel. The implementation of this recycling program is underway at steel plants and the experience of recycling spent refractories will be discussed.

Jan 1, 2002

By C. E. Abbey

Cobalt, iron and manganese play various roles in copper electrowinning using lead–calcium–tin alloyed anodes. Cobalt catalyzes electrochemical water decomposition resulting in lower anode potential and reduced corrosion rates. Iron reduces cathodic current efficiency, but is used to reduce higher oxidation states of manganese that oxidize organics in solvent extraction. Manganese also produces anode scale and is generally considered a problematic impurity. The effect of the combined interaction of these three metal ions on the anode potential has not been quantified yet. The current work used a three factor, two level, three replicate central composite design of experiments to analyze the effects and potential interactions among cobalt, iron and manganese. The experiments consisted of chronopotentiometric analysis to assess anode potential after 24 h of operation. Higher [Co], lower [Mn] and either high or low [Fe] yielded lower anode potentials. Two regression models were developed to predict anode potential as a function of [Co], [Fe] and [Mn]. A method to estimate electrical energy consumption for copper electrowinning is also presented.

By T. Wang, R. G. Reddy, D. Mantha

"A new eutectic LiN03-NaN03-KN03-KN02 quaternary molten salt system was calculated using thermodynamic modeling. The eutectic temperature was predicted to be 100°C. The melting point and heat capacity of the salt eutectic composition were determined using DSC. The experimentally determined melting point is in excellent agreement with the predicted value. The melting point is more than 124°C lower than that of the KN03-NaN03 solar salt. The density of the molten salt was experimentally determined as function of temperature. Using the density, heat capacity and the melting point, thermal energy storage density and gravimetric storage density of the quaternary molten salt were calculated and compared with that of solar salt. The larger storage density value of this molten salt indicates that this salt has a better energy storage capacity for solar power generation systems.IntroductionMolten salts have been used as thermal energy storage media for solar energy applications. Nitrates are being used in the solar energy applications for their low melting point, low unit cost, high heat capacity, high thermal stability, negligible vapor pressure and high energy storage density [l]. Solar salt (NaN03/KN03: 60/40) is the most popular thermal energy storage medium which is currently being used with the freezing point of 221 ·c [2]; another ternary system HITEC® which contains NaN03, KN03 and NaN02 has freezing point of 141°C [3]. Newer nitrate salt mixtures are being studied and projected as potential candidates for thermal energy storage (TES) and heat transfer (HT) applications. Based on these favorable features, molten salt can work directly as the energy storage medium below 500°C [l]. Development and synthesis of newer molten salt mixtures with freezing point lower than those currently used for thermal energy storage applications is necessary for sustained utilization of solar energy. The approach to develop lower freezing point molten salt mixtures is by the prediction of new eutectic mixtures and also by the development of new nitrate compounds."

Jan 1, 2012

By Lv Guozhi, Ren Xiaodong, Liu Yan, Dou Zhihe

"This paper investigated a new desulfurizer, dolomite and ferrosilicon. Magnesium vapor produced by silicothermic reduction of dolomite and ferrosilicon in an immersion tube of molten iron was injected into the molten iron by carrier gas through the underpunch of the tube and desulfurization reaction occurred. In order to explore the desulfurization process of molten iron by the new desulfurizer, the thermodynamics, and experiments of magnesium vapor production and desulfurization have been studied. Through thermodynamic calculation, the reaction temperature of magnesium vapor production by 75ferrosilicon and light-burned dolomite is 1838K in the standard state and decreased with the decreasing partial pressure of magnesium vapor, PMg· When PMg=25kPa, the reaction happens at 1673K. From experiments of magnesium vapor production, reduction efficiency of Mg vapor is about 60 % in 15 minutes at 1673K. From hot metal experiments, the desulfurization efficiency is 89.35%, and the lowest sulfur concentration after desulfurization is 46ppm.IntroductionPretreatment desulfurization of hot metal has become a necessary step in modem optimizing steelmaking process for its cheap cost, which can not only liberate of blast furnace productivity and reduce the burden of produce steel, but also effectively improve overall economic efficiency of the iron and steel system[l-ZJ_ At present, injection magnesium particle is one of the two main methods of desulphurization in hot metal owing to its strong affinity for sulphur, low amount of slag produced, low iron loss in slag skimming and low equipment investment[3l. However, there are still some insufficiencies on the hot iron pretreatment with magnesium particles at present[4-5l"

Jan 1, 2013

By J. Murdoch Mackenzie

Two commercial nickel solvent extraction plants treating laterite leach solutions and using LIX®84-I have been operated in Australia. These circuits employ similar extraction chemistry but differ in their leaching and stripping operations. An alternative process involving elements of both can be conceived. The preparation of the feed solution to solvent extraction plays an important role in nickel extraction using LIX®84-I and the special features of manganese removal and cobalt oxidation in the preparation of the PLS are discussed. This paper compares these three circuit configurations with special reference to the extraction and reductive stripping of cobalt, the transfer of zinc and copper to the strip aqueous, ammonia transfer and sulfur transfer. The potential degradation of the organic and remediation using re-oximation is discussed. Keywords: Nickel, Solvent Extraction, Oxime

Jan 1, 2004

By M. Neises, M. Roeb, C. Sattler, S. Stenger

"A two-step thermo-chemical cycle process has been developed and investigated. It is based on metal oxide redox pair systems, which can split carbon dioxide as well as water molecules by extracting oxygen atoms and reversibly incorporating them into their lattice. If concentrated solar radiation is used as the heat source, a promising method exists to produce synthesis gas from water and CO2. An easy way of operation is gained by the combination of a ceramic substrate as the absorber structure, which can be heated to high temperatures with concentrated solar radiation, and of a metal oxide coating which is capable to carry out the redox reactions. The performance and kinetics of a ferrite based redox material coated on ceramic substrates were investigated in a laboratory set-up. CO2 could be reduced with significant conversions. In addition, several side reactions were observed like the formation of carbon and like the Boudouard reaction.IntroductionThe search for alternative energy carriers and for processes able to reuse carbon dioxide stimulates the research for sustainable routes of alternative fuel production. In the scope of this search thermo-chemical processes combined with sources of concentrated solar energy have become more and more attractive. Ideally, the only raw materials for such processes are water (H2O) and carbon dioxide (CO2) enabling not only a process free of emissions, but also allow to reduce emissions of other processes by reusing CO2 to provide synthesis gas, which itself can be applied to produce chemical commodities or even better synthetic fuels like methanol or petrol.In contrast to the direct splitting of those raw materials, thermochemical cycles split water and CO2 in several steps and enable hydrogen (H2) and carbon monoxide (CO) generation at temperatures controllable by today’s technical equipment. One of the most interesting thermochemical cycles is a two-step process using metal oxide based redox systems. During the first step of this cycle (the regeneration step) the metal oxide is reduced setting some of its lattice oxygen free according to reaction (1). In the next step (the splitting) the reduced and activated material is oxidised by withdrawing oxygen from water and CO2 and at the same time hydrogen and CO is set free according to reactions (2a) and (2b) respectively."

Jan 1, 2011

By Jillian Spindura

This work investigates the carbothermic reduction of the complex sulphide mineral, pentlandite, in the presence of lime. The effects of change in temperature and the use of different carbon sources are studied and the role of these variables on the reducibility of pentlandite mineral is discussed. The microstructures of the heat-treated pellets are examined using X-ray diffraction and scanning electron microscopic techniques. The latter analytical method also allows any variation in the morphology and composition of the metallic phases formed, with temperature, to be considered. The kinetics of the reduction process is studied and the magnitude of the overall activation energy is determined from the plots of percentage reduction versus time.

Jan 1, 1996

By Marcio B. Fonseca

Nickel-cobalt laterite deposits have become the focus of attention for hydrometallurgical processing. Following the lessons of the second generation high pressure acid leach (HPAL) projects in Western Australia other Ni-Co laterite projects are now evaluating potential HPAL projects with a rigorous integrated approach that begins with geological modeling, resource estimation and metallurgical studies. The Vermelho nickel-cobalt laterite deposit has been under exploration and study for several years with investigations of various metallurgical processes. Recent HPAL studies have indicated that the nickel and cobalt laterite at this deposit is amenable to upgrading by silica rejection followed by pressure leaching. These studies have required a detailed geological investigation to generate a new resource model. The recent development of a sophisticated geological model integrated with a multi-element resource estimation for this complex tropical nickel laterite deposit in northern Brazil provides an example of the contribution of geology at the critical project stage where process technology decisions are made on relatively small samples of the total resource.\ Keywords: Ni Laterite, Geological Modeling, Resource Estimation

Jan 1, 2004

By Liugen Sun, Xingming Jiang, Weijiao Yang, Yihang Hu, Yongqiang Yang, Hua Wang

During the past decades, cyclone electrowinning (CE) has been regarded as a novel separation technology, which can be used for direct electrowinning of metals from low concentration solution. Recently, CE was proven effective for the treatment of antimonic gold concentrates. The experimental results of cyclone electrowinning of antimony show the current efficiency increases from 43.8 to 72.2% with the increasing current density (from 254.8 to 647.3 A/m2), and on the other hand, power consumption per ton antimony decreases from 6100 to 4200 kWh with the aforementioned increasing current density. The grade of the obtained cathode antimony could reach 98.6%. Compared with the traditional electrowinning using parallel-board electrodes, the economic profit of CE was 33.1% higher attributed to the high current efficiency of CE. In addition, CE could adapt to high current density. All these characteristics indicate the CE method can be implemented commercially for processing antimonic gold concentrates.

Mar 1, 2018

By Pedro Lobarinhas

In the present work a two dimensional computational model is derived for the description of the time dependent heap leaching process. The flow inside the heap is calculated using the diffusion equations for the flow in porous media. The soil conductivity is also estimated assuming a close packed structure for the grain packing inside the heap. These equations, with appropriate boundary conditions, are solved using a time step splitting scheme. From this calculation the amount of leaching reagent in contact with the ore at any position inside the heap can be calculated and, once coupled with appropriate reaction equations, the amount of metals extracted can be computed and leaching agent concentration updated. The model is tested with available experimental data and the results have shown to be in a very good agreement. The model predicts all the transient features of the data.

Jan 1, 1999

By Ray Y. Lin, Sunil G. Warrier

"Low cost processing of metal matrix composites is an essential requirement for this class of materials to be acceptable in commercial application. In an effort to reduce the cost of processing of metal matrix composites, an infrared pressureless liquid infiltration technique has been developed. The salient features of infrared infiltration are that it is rapid, simple and a low cost process. The rapid processing capability causes very little oxide formation on the alloy resulting in both improved wetting and flow characteristics and reduced oxygen contamination in the composite. Thus, vacuum is normally not required. Using infrared inflltration, aluminum and titanium matrix composites have been prepared under an ambient argon atmosphere. Reinforcements in these composites include carbon fibers, silicon carbide Nicalon fibers and Textron's SCS fibers. Microstructural and mechanical test results indicate that completely consolidated composites with good fiber distribution, limited interfacial reaction and high mechanical properties can be manufactured by this process. IntroductionAluminum and titanium matrix composites reinforced with ceramic reinforcements are strong candidates for numerous applications in the aerospace and automotive industries. Aluminum matrix composites are commonly fabricated by either solid state vacuum hot pressing, liquid state pressure infiltration or squeeze casting [1]. Although liquid state pressure infiltration and squeeze casting has significant advantages over solid state processes, the requirement for pressure makes these composites uneconomical for large scale industrial application. Titanium matrix composites are primarily fabricated by solid state diffusion bonding [2]. Pressureless liquid infiltration can significantly reduce the cost of fabrication in both the composite systems. However, during pressureless infiltration processes, several complications concerning the wetting characteristics and chemical compatibility arise."

Jan 1, 1994

By F. T. Principe

In order for solvent extraction technology to be acceptable as an alternative to existing jarosite precipitation circuits, iron must be cleanly separated and concentrated into a feed stream suitable for downstream iron by-product recovery which meets market specifications and economics. Ten years ago, significant progress was made in a joint McCill University/CANMET project that involved iron extraction with mono(2-ethylhexyl) phosphoric acid and stripping with HCI. Our iron solvent extraction research was reactivated recently by looking into this and other members of the organophosphorus extractant family. Our research focuses on the mechanisms and control of anion (SO42/CI) transport across the various phases (Rafinate/Organic/Strip), iron build-up in the strip liquor, and extractant stability/selectivity. In this paper, these issues along with some other performance parameters are discussed using data derived from an extensive search of the two commercially available and best known members of the organophosphorus family, di-2-ethylhexyl (D2EHPA) and mono-2-ethylhexyl (M2EHPA) phosphoric acid. Further in this discussion, the challenges lying ahead in the development of sx systems that overcome the deficiencies of D2EHPA and M2EHPA are outlined. In particular, the necessity of considering secondary separation technologies that can further concentrate iron values in the chloride strip liquor to levels economically attractive for the production of saleable iron oxide by pyrohydrolysis is addressed.

Jan 1, 1998

By Chang-Young Choi

Korea Zinc commenced zinc production in 1978 with a capacity of 50,000 tpa. Since then, continuous investments have been made and resulted in Korea Zinc now being the biggest zinc and lead producer in the world. In the course of increasing zinc production capacity, the company management realized that the company needed a lead smelter to prevent the solid waste disposal problems by treating the lead containing solid waste. This paper begins by briefly stating the objectives and the roles of the lead smelter at Onsan. It describes the QSL process and the TSL process, and further extends the description of the TSL process, through which harmless inert solid waste could be produced for secure final disposal. It is also mentioned that the TSL process plays an important role in the integration of zinc and lead production. Throughout the paper, a positive attitude in handling the environmental issues in the non-ferrous smelting industry is emphasized. Finally, a solution for the solid waste disposal problem in the zinc and lead industry is proposed, with which the environmental issues can be an opportunity rather than a crisis. The current operation at Onsan suggests the future direction of the non-ferrous smelting technology that all of the zinc and lead producers should pursue.

Jan 1, 2003

By Chang-Young Choi

Korea Zinc commenced zinc production in 1978 with a capacity of 50,000 tpa. Since then, continuous investments have been made and resulted in Korea Zinc now being the biggest zinc and lead producer in the world. In the course of increasing zinc production capacity, the company management realized that the company needed a lead smelter to prevent the solid waste disposal problems by treating the lead containing solid waste. This paper begins by briefly stating the objectives and the roles of the lead smelter at Onsan. It describes the QSL process and the TSL process, and further extends the description of the TSL process, through which harmless inert solid waste could be produced for secure final disposal. It is also mentioned that the TSL process plays an important role in the integration of zinc and lead production. Throughout the paper, a positive attitude in handling the environmental issues in the non-ferrous smelting industry is emphasized. Finally, a solution for the solid waste disposal problem in the zinc and lead industry is proposed, with which the environmental issues can be an opportunity rather than a crisis. The current operation at Ousan suggests the future direction of the non-ferrous smelting technology that all of the zinc and lead producers should pursue.

Jan 1, 2003

By G. Diáz

The PLACID process applied to the recycling of spent lead-acid batteries is being developed by an European Consortium within the Brite-Euram II programme. The status of the project entitled "Lead Recovery from Lead Oxide Secondaries" is described in this paper. The main laboratory and batch experimental results and the preliminary feasibility study are summarised. The description of the demonstration pilot plant and continuous campaigns programme for 1995 are also included. An interesting global approach is proposed, integrating the Placid process in the existing spent battery recycling pyrometallurgical facilities. This yields important improvements in the overall process. Grids would be easily treated by the conventional pyrometallurgical route, obtaining lead alloys,, while battery pastes, slags and fumes would be fed to the Placid process, obtaining pure electrolytic lead (>99.99 %), ideal for battery paste manufacturing. The implementation of the Placid process into the existing battery recycling pyrometallurgical facilities is analyzed from technical, environmental and economical viewpoints. Greater overall lead recovery, lower operating costs, reduced waste production, environmentally safer residues and much better lead product quality are the key advantages. The authors draw the following final conclusion : Integration of the Placid process with conventional pyrometallurgical treatment is a feasible and very attractive alternative route for spent lead-acid battery recycling.

Jan 1, 1995