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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 C. Koopman

During the production of phosphoric acid from phosphate ore and sulfuric acid, large amounts of calcium sulfate are formed, in which impurities from the feedstock are incorporated. To use the calcium sulfate in, for example, the building industry, a lower concentration of impurities is desired. Mercury, copper, lead, and cadmium were extracted from clear industrial recrystallization acid (0.8-3.9 mol/kg H3PO4, 0.2-0:5 mol/kg H2SO4) by supported solvent extraction with the extracting agent Cyanex 302 in kerosene in a transverse flow hollow fiber module. The permeability for the mercury ion was 1.4.10-6 m/s, whereas that for the copper ion was calculated to be 1.5.10 m/s. Cadmium, lead, and copper were extracted during the recrystallization of calcium sulfate hemihydrate to dihydrate, an existing step within the ,phosphoric acid production process, by solvent extraction with the same extracting agent. The concentrations of cadmium and zinc in the newly formed calcium sulfate were proven to be decreased. Unfortunately, concentrations of mercury and lead were too low for analysis.

Jan 1, 1999

By Lucas Nana Wiredu Damoah, Lifeng Zhang

"The use of electromagnetic field to remove suspended particles from metals such as aluminum by pushing to the boundary has been well studied. However, the potential of this method is yet to be exploited for the removal of inclusions from silicon. Considering the increasing amount of Top-cut SoG-Si scraps year upon year, there is the need to harness all the potentials of technologies to recycle this materials to ensure sustainability. This study investigates, and discusses new results on the effect of processing parameters such as composition, coil current, and frequency on the removal of inclusions from silicon under high frequency AC electromagnetic field.IntroductionThe solar cell silicon making industry requires pure and clean silicon in order to maximize the conversion potential of the solar cell material. The conversion efficiency of solar cells is limited by minority carrier recombination at dislocations and those intra-granular defects such as impurities, small clusters of atoms, or precipitates [1]. Recent global developments in the energy sector with a drive for the production of clean, reliable, and affordable energy have stirred a rapid growth in the production of photovoltaic (PV) cells.[2] Thus over the years, silicon based PV cells has seen a lot of growth as it has a PV market share of over 90 % [3] either as single-crystalline silicon, or multi-crystalline Si (MC-Si), or amorphous Si [4]. MC-Si produced by directional solidification of solar grade silicon melt dominates the silicon PV market. During the directional solidification process, SiC and Si3N4 particles within the melt are pushed by the solidification front to the top of the ingot which is the last to solidify. Therefore the top of the ingot is cut generating what is known as top-cut solar silicon scraps. The Si3N4 particles are mainly from the coating material at the inside surface of the silica crucible and from the air absorption during solidification process. The SiC particles mainly stem from the carbon reduction process of the primary production of silicon [5]. For sustainability the silicon in the top-cut silicon scraps must be recovered. Therefore methods for removing non-metallic particles, such as SiC and Si3N4, from the silicon are important in order to recycle the top-cut scraps to a useful feedstock for the silicon solar cells manufacturing."

Jan 1, 2012

By J. M. D. Wilson

An analytical program using a combination of SEM-based image analysis techniques is developed for automated modal analysis of ores containing silicate and other gangue minerals. Previous knowledge, gathered by means of either optical microscopy, X-ray diffraction, SEM, or electron microprobe analysis is used to establish discrimination criteria in the image analysis program. The program initially discriminates minerals on the basis of their relative grey values in a backscattered electron image. For those minerals which have overlapping grey levels the minerals are identified by the program using energy dispersive X-ray spectrometry with X-ray counting for twelve or more elements. This technique is useful to quantify ores in which the gangue minerals are numerous. Two cases of application are presented.

Jan 1, 1999

By Sumantra Mandal

The hot deformed microstructure of the 15Cr-15Ni-2.2Mo-Ti modified austenitic stainless steel (commonly known as alloy D9) was investigated employing electron backscatter diffraction (EBSD). Hot compression tests were conducted in a Gleeble thermo-mechanical simulator at temperatures of 1173K-1373K (in steps of 100K) with a strain rate of 10 and 100 s-1 to different strains. Various kinds of deformation patterns were observed inside the deformed grains. These were inferred as the development of geometrically necessary boundaries or formation of parallel set of micro-bands. Recrystallized grains were partitioned from the deformed grains employing grain orientation spread approach. Extent of dynamic recrystallization (DRX) was found to be minimal at 1173K. DRX was predominantly found to happen at and above 1273K which increases with increase in strain. DRX nucleation and development mechanisms were discussed with respect to bulging of the parent grains and sub-grain rotation. Special emphasize is given on the role of annealing twins on DRX nucleation and subsequent expansion.

Jan 1, 2009

By R. I. Rodriguez

Since the 1973 energy crisis, high fuel oil costs have been eroding the economics of the Nicaro and Punta Gorda Plants that employ the Caron Process for laterites processing. Since 1995, Cuban crude oil production has growth dramatically, with progressive utilization in power generation, cement and nickel plants. This paper shows how Nicaro and Punta Gorda plants have been able to shift from expensive Bunker C Fuel Oil to heavy but cheaper Cuban Crude Oil of high Sulfur content and achieve a significant reduction in operating cost. Problems related to the high sulfur content of the Cuban crude oil have demanded extensive investigations of the process chemistry and novelty solutions are proposed, with corresponding changes in process conditions. Innovative options are shown that will allow further cost reductions in the future. Keywords: Cuban Crude Oil, Sulfur, Ammonia.

Jan 1, 2004

By Chao Lian, Hongxu Li, Hao Bai, Wei Wei

"Application of high-emissivity coating on inner walls in industrial furnaces increases the furnace thermal efficiency. The coating with high emissivity strengthens radiation heat transfer in the furnace, however, according to Wien's displacement law and Planck's radiation law, under heating temperature, the wavelengths of the radiation transfer are mostly between 1-5 µm, implying that increasing emissivity of the coating in near infrared band is more effective for higher thermal efficiency. In this paper, a new CuO-ZnO-based coating material sintered at 1600K was developed. The emissivity of the samples were measured and the result shows that, in near-infrared band, the emissivity of the sample reaches 0.98 at 773K with 13at.% of CuO doped in ZnO. In addition, the effects of CuO doping and use temperature on emissivity were also discussed. Furthermore, crystallization behaviors of ZnO-CuO sintering were investigated by DTA,XRD and SEM-EDS etc., which offered information for possible optimal design of the material.1. IntroductionIndustrial furnaces are widely used in various industrial heating. For example, the metal smelting furnace, ore sintering furnace in metallurgical industry; the distillation furnace, cracking furnace in petroleum industry etc,. The research on efficient energy saving technology has important significance. High emissivity coatings are widely used in many high temperature applications to effectively transfer the heat by radiation [ 1]. The theoretical calculation and experimental studies have shown that, coated high emissivity coating in the heating surface is an effective method to enlarge the infrared radiation power [2].At present, the infrared high emissivity coating has been widely used in China, and have been achieved remarkable energy saving effect. According to Wien' s displacement law and Planck' slaw, most energy of the black body at high temperature is radiated in the wavelength range of l-5µm; however it happens that many materials have the low emissivity within this range. Thus, it is important to improve the near-infrared band emissivity of materials [3]."

Jan 1, 2013

By Xin-liang Gao, Qing Li, Gui-qin Fu, Duo Jin, Miao-yong Zhu

"Optical microscope together with alternative wet-dry cyclic accelerated corrosion tests and XRD, SEM were employed on bridge weathering steel samples with different Mn and Ni contents which were vacuum induction melted and rolled to study their effects on the microstructure and rust layer evolution in er' containing condition. The results show that the microstructure is mainly ferrite and pearlite when Mn and Ni contents are 0.75 %, 0.42 %, respectively. Both the increase of Mn and Ni contents will make pearlite disappear while granular bainite appear, meanwhile the grain size decreases. With the increase of Mn content, the corrosion rate decreases in the initial stage, but the effect becomes little in the later stage. The increase of Ni not only improves the corrosion resistance of steel base at the initial stage but also hinders the tendency of further corrosion. As Mn content increases, a-FeOOH contents in rust layer decreases. With increase of Ni content, the content of a-FeOOH in the rust increases while that ofy-FeOOH decreases.IntroductionWeathering steels had been ~radually applied in manufacture of bridges owing to reducing the corrosion rate remarkably [I- l .Good weldability was needed for high performance bridge weathering steels. Since carbon was thought to be bad for weldability, low carbon content steel was adopted and Mn was added to amend the mechanical strength loss. Some scholars[6, 7l believed that Mn was beneficial for increasing corrosion resistance performance of the steel in marine atmospheric environment. Some scholars [S, 9l thought that Mn had little effect on corrosion resistance in marine atmospheric environment. Presently, the effect of Mn on bridge weathering steel in marine atmospheric environment still remained poorly understood. Ni was considered to be beneficial for increasing corrosion resistance performance in marine atmospheric environment [JO-l4l However, the high cost limited its application range. What would bring to the rust and corrosion by decreasing Ni content needed further research.Most researchers assumed that microstructures only affected the corrosion behavior of bare steel. But the study of Guo et al. P5l showed that the homogenous microstructures were beneficial for the corrosion resistance of steels. The effect of Mn, Ni content change on microstructure and microstructure on corrosion still remained poorly understood. In the present work, the effect of Mn and Ni on the microstructures of steel matrix, as well as the microstructures on the rust and corrosion was investigated."

Jan 1, 2014

By Judy Che, Steven Ceccio, Gretar Tryggvason

"A detailed understanding of drop deformation and solidification is essential for quantitative predictions of geometry and properties of parts made by ballistic particle manufacturing processes. Axisymmetric results of towers built by the deposition of multiple drops are presented. In these computations, fluid flow, heat transfer, and phase change are fully coupled throughout the drop deformation and solidification process. The solution method is based on a single set of conservation equations written for all phases simultaneously. The phase boundaries are treated as imbedded interfaces by adding the appropriate source terms to the conservation equations. A parameter study demonstrates the effect of Weber number, Peclet number, and drop deposition frequency on the final shape of the structure. Numerical results show that most successful method of building uniform towers is when two conditions are met. First, each drop solidifies at the same time in the deformation cycle. Second, the cooling rate is slow enough to allow for good adhesion between drops. The ability to predict the final shape of deposited drops will greatly reduce the amount of experimentation necessary to select the desired set parameters for any artifact.IntroductionMaterial deposition techniques based on layering small molten metal drops holds the promise to build small, coherent three-dimensional structures. In this process, numerous 20-100 µm diameter drops are deposited onto a substrate with a low impact velocity (on the order of 5 mis). Both the momentum and trajectory of each drop are controlled precisely to build up complex parts. This material layering technique differs from processes such as spray forming and splat quenching which involve high impact velocities (on the order of 100 mis) and high frequency deposition with little control over individual drop placement. This process of layering small drops can produce parts with near net shape accuracy, while spray forming produces slabs of material which must then be worked to make a usable part. The ability to computationally predict final drop shape and cooling rate has the advantage of allowing the user to select parameters to produce parts with desired shape and mechanical properties. However, the development of such predictive methods requires a thorough understanding of both drop deformation and solidification"

Jan 1, 1999

By Mao Chen, Baojun Zhao, Zhixiang Cui, Leonel Contreras

Viscosity is one of the important physiochemical properties of metallurgical slags which is important for slag tapping, metal loss in slag, freeze lining and fluid dynamics. High temperature viscosity measurements are time- and cost-consuming and the number of experiments is limited. Viscosity model is an effective way to predict the viscosities of the complex slags at high temperature. However, a reliable viscosity model can only be developed on the base of accurate experimental data. A unique high-temperature viscosity measurement apparatus developed at The University of Queensland enabled accurate viscosity data to be measured for the “FeO”-SiO2-CaO-MgO-Al2O3 system in equilibrium with Fe. An accurate viscosity model has been developed based on Eyring’s theory and extensive viscosity measurements. The viscosities of copper smelting, converting and cleaning slags over a wide range of compositions and temperatures can be predicted and applied in the process control.

Jan 1, 2016

By G. Gomathi, K. Asokan, K. Subramanian

An electrochemical reactor with anode and cathode chambers separated by a composite perfluoro polymer cation exchange membrane was designed, fabricated and used for the reduction of dissolved carbon dioxide under ambient conditions to formate. The flow reactor enhanced the mass transfer of carbon dioxide compared to the batch reactor. Experiments were conducted using two different perfluoro polymer membranes - Nafion 961. Efficacy of CO2 reduction on various cathode materials (Cd, Pb, Sn and Zn plated stainless steel woven mesh) were determined. Optimum values of flow rate and current density were evaluated for the energy efficient formation of formate in aqueous KHCO3 (pH 7.5-8.5) buffer solutions.

Jan 1, 2008

By Cindy L. Williams

"The Blue Star subdistrict in the Carlin Trend, Nevada, includes multiple mines with 33.9 t Au in reserve and past production totaling 89 .1 t Au. The deposits are characterized by zoned alteration mineralogy and gold grades. From orebody centers outward the zones include: 1) a silicified core with erratic gold grade; 2) adjacent mill-grade (> 1.37 Au git) intense quartz-sericite-pyrite alteration; 3) enveloping leach-grade (0.21 Au g/t to 1.37 Au git) weaker sericite-kaolinite-quartzpyrite alteration; 4) surrounding decarbonatized and intensely argillized waste and leach grade ore; 5) pervasively decarbonatized waste rock; and 6) peripheral waste with weak decarbonatization and local propylitic alteration. Zoned alteration extends as much as 1500 m beyond orebodies.Understanding Blue Star subdistrict zoned alteration assemblages and gold grades has increased geologists' ability to provide practical and economically significant information to geotechnical engineers, mine planners and drill and blast personnel. Alteration influences geotechnical pitslope design because each assemblage has distinct rock strength. Geotechnical engineers use three-dimensional models of incompetent alteration types as a foundation for pit-slope design. In the drill and blast cycle, hard and soft alteration types require modified practices (powder column, blast hole spacing, delay design etc.) for optimum blast energy distribution. Further, geotechnically instable alteration types require careful blast procedures to prevent backbreak whic~ damages ultimate walls. In addition to mine planning and mining applications, zoned alteration assemblages extending beyond orebodies provide a useful exploration guide. Metallurgical character also varies with alteration type. Intensely quartz-sericite-pyrite altered or silicified ore has relatively high partical-size dependency and poor leach recoveries. Moderately sericite-kaolinite-quartz-pyrite altered rock, in contrast, shows little size dependency and good leach recoveries.The author sincerely thanks L. Schutz, P. Williams, C. Clode, W. Trudell, P. Herrera, M.DKunkel, M. Goings and numerous other Newmont geologists, metallurgist, engineers and support staff who made this paper possible."

Jan 1, 1997

By X. Jay Gao

A fast high-temperature carburizing process integrated with materials design and optimization via a systems design approach was developed to significantly reduce process cycle time. Process experiments were focused on boost cycles to obtain a robust boost process and investigate surface reaction kinetics, primary carbide formation and dissolution. Weight gain and microhardness were measured, all showing evidence of non-monotonic time evolution for longer boost times at higher temperatures. Optical and electron microscopy and other techniques have been used to identify possible carbides, their location and types. These results assist the picking of first boost time with least variation rate in terms of content of case carbon and carbides, dissolvable in subsequent diffuse if any. The results also provide critical information to properly formulate surface reaction kinetics and diffusion and formation kinetics of carbides modeled using DICTRA. Keywords: high temperature vacuum carburizing, partial pressure carburizing, heat treatment, process development, carbide, case hardening, microstructural analysis, over carburizing

Jan 1, 2003

By C. Alexandru Sonoc

Donnan Dialysis uses ion exchange membranes to extract and separate cations. The driving force is provided by differences in chemical potential, rather than by electric fields or pressure. A Donnan Dialysis based process to recover lithium, nickel, cobalt, manganese, and organic acid lixiviant from recycled lithium ion battery cathodes is under development. In this paper we present a model of Donnan Dialysis and results of simulations of the aforementioned process. The simulations show that 170 m2 of membranes can process 1000 L of leachate ([Li+] = 0.285 M, [Co2+] = [Ni2+] = [Mn2+] = 0.095 M, pH 2) in two days and recover 94.1% of the lithium (as lithium carbonate), 99.4% of the transition metals (as mixed sulphates ready for solvent extraction), and all of the organic acid using 423 mol of H2SO4 and 268 mol of KHCO3.

By C. Liliane Carvalho

In the current study, bio-oxidation tests were carried out in shaking flasks with a flotation concentrate containing the sulphides pyrite, arsenopyrite and gudmidite. The tests were performed with mesophilic microorganisms (At. ferrooxidans) at 30 °C and also with the moderate thermophile S. thermosulfidooxidans, at 50 °C. The effects of (i) previous adaptation of the microorganisms to the concentrate, (ii) ferrous iron concentration and (iii) pulp density (2%, 4% and 6% (w/v)) on the dissolution of the sulphide were studied through arsenic extractions. S. thermosulfidooxidans was more sensitive to the pulp density in comparison to At. ferrooxidans as a reduction in sulphide oxidation was observed with the increase in the solid content to 6%. Therefore, the mesophilic strain was selected for further work, which comprised a rolling bottle experiment at 10% solids. After 40 days of bio-oxidation, the solid material was subjected to cyanidation, which revealed 85% gold extraction as compared to 21% from the original concentrate. The antimony sulphide grains in the bio-oxidized product showed similarity to what was observed in the original sample, suggesting such particles were not susceptible to the bio-oxidation process.

By David Tisdale, Phillip Mackey, Nagendra Tripathi, Matthew Kreuh, Pascal Coursol

Xstrata Nickel’s Sudbury smelter operation is based on fluid bed roasting of Ni-Cu sulphide concentrate, followed by electric furnace reductive smelting and Peirce-Smith converting to produce a Bessemer matte for electro refining, along with sulphuric acid produced from smelter gas. While the site dates back to the 1930s, the present smelter configuration has been operational since 1978, and currently has a nominal capacity of about 67,000 tpy of contained nickel and is investigating options to expand in future up to 85,000 tpy. As part of a review of plant capacity options, a new metallurgical model of the plant was developed in order to examine a number of processing alternatives. Based on the METSIM™ platform, the present model includes the ability to examine the impact of a number of plant parameters on potential plant performance including; for example, the following: percent of sulphur elimination in roasting, matte grade, degree of matte metallization, temperature, coke requirements, sulphuric acid production, CO2 emissions and overall energy requirements. The process model also includes a number of special features adopted; for example, approaches to effectively model the complex Ni-Cu-Co-Fe-S-O matte system. This paper provides a description of the model and gives an overview of the results. As well as presenting the results of the present study, the applicability of this modeling approach to pyrometallurgical systems in general is also briefly discussed in the paper.

Jan 1, 2009

By P. M. Tait, N. A. Warner

"The refining of thermally produced zinc is currently performed using a highly energy intensive and arguably outmoded process, distilling zinc under atmospheric pressure at temperatures of 900°C to 1000°C. In order to produce refined zinc more profitably and with less environmental impact a new process has been proposed. This process is generic to all thermal zinc smelters and aims to match the purity of zinc from current technology (99.99%-99.999%). The objective is to perform all separation processes using only the heat contained in the smelter product stream. Vacuum conditions are extensively used lowering operating temperatures and enhancing separations. As part of this process zinc is distilled under vacuum from high concentration obtaining a refined product with respect to lead content. A mathematical model has been developed from fundamental principles to describe this stage, the distillation of zinc across a temperature difference between two circulating zinc streams in open channels under vacuum. Heat for the distillation is supplied by the liquid phase, necessitating a large recycle to maintain high operating temperatures, and keep zinc concentrations high. In determining this model and the operating conditions required, relationships between temperature, pressure and composition are considered.IntroductionCurrent technology (the Refluxer) used to refine thermally produced zinc is both expensive and highly inefficient. At present 80% of the worlds zinc is produced via the electrolytic process reflecting the poorer performance of the thermal route, the zinc-lead blast furnace and Refluxer. A new process is proposed to overcome the drawbacks of current processes. These drawbacks are both economic and environmental. The Refluxer requires 6.6 GJ of energy to refine one tonne of SHG zinc 1, other disadvantages of the Refluxer stem from high operating temperature, around 900°C, and liquid zinc being highly corrosive towards ferrous metals. The Refluxer is constructed from silicon carbide sections which join together by means of flat machined faces making liquid metal leaks inevitable. The Refluxer columns are very sensitive to thermal cycling, thermal shock and mechanical vibration, which easily lead to structural failure. To avoid thermal stress on the columns the feed rate and feed temperature need to be kept constant which means the feed baths to the columns must be able to accept solid and liquid feed as the Refluxer has to operate when the smelter is shut down."

Jan 1, 1998

By Eltefat Ahmadi

Iron-free titanium oxycarbonitride (TiOxCyNz) is a promising feedstock for production of titanium tetrachloride (TiCl4) at low temperatures. In this study, the effects of leaching variables such as temperature, time, particle size of staring material and concentration of the leaching solutions were evaluated on iron removal from nitrided Malaysian ilmenite by Becher process. The nitrided ilmenite was prepared by isothermal reduction with graphite at 1200 °C for 3 h in H2-N2 atmosphere. The aerated leaching experiments were conducted at 50–90 °C with addition of 0.3–2.0 wt% of NH4Cl catalyst. The highest extent of iron removal (XFe) was obtained at about 96.2% for the sample leached at 90 °C for 7 h with 2.0 wt% NH4Cl. The iron concentrate and titanium oxycarbonitride product were characterized by ICP-OES, XRD, XRF and SEM-EDX analyses. The results indicated that the aeration leaching process was a successful route to prepare low-iron titanium oxycarbonitride.

By Roberto Javier Santiago

This paper tries to make a study about the use of calcium carbide during the tapping in replacement of part of the aluminum used in the furnace tapping, analyzing theoretical consumptions and then transfering the practice to the plant.

Jan 1, 2006

By Hong Yong Sohn

On the occasion of this symposium in my name, I reflect upon the contributions of my academic mentors and early associates who helped shape my professional career. I was fortunate to have these people around me during my graduate work and at the start of my professional career. In forming my view of the technical field and career, they represented academia, research institutions, industry, and different parts of the world.

Jan 1, 2006