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By Eduardo Juncal, Jorge Alberto Soares Tenorio, Jose Roberto de Oliveira, Denise Crocce Romano Espinosal

"Steel industry has been expanding every year, consequently there has been an increase in waste generation in this area. Thus, companies in this sector are finding it difficult to give a correct destination of waste. For example, only in a basic oxygen furnace (BOF) converter are generated about l8kg of dust per ton of steel. The aim of this work was the characterization of dust generated in the BOF converter. The characterization was performed by chemical analysis (titration for iron and its oxides and Inductively Coupled Plasma Atomic Emission Spectroscopy for other elements), scanning electron microscopy, size analysis using Mastersizer 2000 equipment and X-ray diffraction. It was observed that dust is composed mainly iron in form of magnetite, metallic iron and wustite with approximately 99% of the particle size below 100 µm.IntroductionToday, steel is a important metal for the world. It can be produced for two routes, blast furnace/ basic oxygen furnace (BOF) converter and electric arc furnace (EAF) [1].First route, the iron is produced from the reduction of iron ore and coke for fuel injection and! or natural gas for a production of pig iron in blast furnace. The pig iron is sent until BOF converter to perform the blowing of oxygen to obtain the steel. In the second route, the steel is produced using scraps or direct reduced iron (DR!) using electric arc.During steel production are generated a lot of wastes like slag, sludges, scraps and dust [2]. Only in the first six months of201O, world steel production totaled 706 million tons [3]. According to Watson and Wang [4], some 10 to 20 kg of dust is generated per tonne of liquid steel produced. Thus, the reuse of these wastes can be a great to companies, because it reduces the amount of raw material to be extracted and reducing disposal costs [5,6]."

Jan 1, 2012

By R. W. McCallum, B. Jensen, K. W. Dennis

"There are substantial challenges in the exploration of magnetic materials in the R-TM-X system (R =rare earth, TM= transition metal, X =stabilizing element) where Xis an element which has high vapor pressure, high reactivity, toxicity, or a refractory nature. This research focuses on discovering new phases with high anisotropy and high magnetization through closed diffusion couples inside high purity Fe crucibles. Either vapor-solid reactions or powder metallurgy techniques are then employed to isolate a stoichiometric sample based on a potentially magnetic phase found in the diffusion couple. For this research, X = F, Ca, Sr, Se, Zn, Bi or Cd, TM= Fe, and R = Nd. New ternary phases have been discovered with WDS and EDS, and magnetic transition temperatures have been measured with a SQUID magnetometer and VSM.IntroductionSince the discovery of the RCo5 compounds in the 1960s, rare earth- transition metal (R-TM) magnets have been the main focus of permanent magnetic research over the last five decades. Iron-based magnetic materials were studied next in attempts to avoid the unstable price of cobalt as well as the high price of Sm, the top performer in the RCos and RzC011 series. This hunt eventually led to the discovery of Nd2Fe14B with a theoretical BHmax of 64 MGOe, nearly double that of the previous samarium based magnets. The next few decades were devoted to enhancing the magnetic properties ofNd2Fe14B by the improvement of processing techniques and the additions of alloying elements. The only complete elemental substitution discovered in this system was R1Fe14C, which did not improve magnetic properties. It is probably safe to say that most ternary R-TM-X systems, where Xis any element that may stabilize a ternary phase, have been investigated if they may be prepared by conventional processes such as arc or induction melting. The present study offers a systematic approach to developing a novel diffusion couple technique in which the volatile, reactive or toxic alloying elements are laser welded inside a high purity Fe crucible. This experimental setup will prevent the oxidation of the rare earth element, as well as contain the volatile X element. As the goal of the research was to find new rare earth permanent magnets, only phases which contained greater than 60 wt% Fe were investigated. 247"

Jan 1, 2012

By G. P. Chaudhari, F. Warchomicka, M. Dikovits, V. Pancholi, C. Poletti

"The hot formability of a microalloyed steel with 0.16 wt-%C modified with N is studied by using processing maps. Compression tests of cylindrical samples are carried out using a Gleeble®3800 simulator in the range of temperature between 750 -1000°C and strain rates between 0.01-100 S-1. For this alloy, an Ar3-temperature about 740°C is determined by means of dilatometry. Processing maps are calculated using the modified dynamic material model developed by Murty and Rao for different logarithmic strains. For the instability map, the parameter Kj developed by the authors in previous works is used and compared with other instability values. Softening in the flow curves provoked by induced ferrite during deformation at low temperatures and low strain rates is reflected in the n-value. Light optical microscopy (LOM) and electron back scattered diffraction (EBSD) measurements are used to study the microstructure of the hot deformed samples to determine the deformation mechanisms active and to verify the processing maps.IntroductionProcessing maps offer a good possibility to optimize thermomechanical process parameters and to avoid defects in the products. Prasad et al. [1] developed the processing maps using the dynamic material model (DMM) and Murty & Rao [2] modified it. Processing maps consist of two superimposed maps: the dissipation efficiency and the instability map. The processing maps can be used to detect areas with a good hot formability, which are normally related to restoration of the material by dynamic recovery/recrystallization. For a high dissipation efficiency value and no instabilities, a good hot formability is predicted. In the DMM no storage of energy takes place and so the material is considered essentially dissipative, this is only true for high temperatures and high strain rates [1]."

Jan 1, 2012

By Xiangru Chen, Honggang Zhong, Qijie Zhai, Qingqing Sun

"A horizontal directional solidification equipment, with an in-situ pouring system, was employed to physically simulate the solidification behavior of continuous casting. In this paper, the 2304 duplex stainless steel (DSS 2304) was investigated using this equipment due to its microstructure produced by continuous casting process was usually not satisfied. The grain size combined with the position of columnar to equiaxed transition (CET) of DSS 2304 were observed and the results showed these microstructure characteristics were very close to those of the continuous casting slabs. In addition, the influences of pouring temperatures and cooling conditions on the CET behavior were investigated. The results revealed that the length of the columnar grains decreased with decreasing the pouring temperatures and flow rates of the cooling water. Besides, the content of austenite decreases with increasing the distance from the chilled sidewall.IntroductionDuplex Stainless Steels (DSSs) have been widely used in industry for their excellent mechanical strength and superior corrosion resistance in Cl- environments when compared with other stainless steels [1,2]. Their good performances are mostly on account of the duplex phase structure-ferrite (d) and austenite (?) and the high proportion of alloying elements. Although, DSSs have good ductility, but worse formability compared to the austenitics, and this is the key to restrict DSSs application [3]. This is due to the differences properties between the two phases. The hot workability of ferrite (d) is better than austenite (?) and exhibits a lower flow stress during hot rolling processing [4]. The early workers had revealed that coalescent force of phase interface, microstructure, difference of mechanical property between two phases and the precipitations are the main factors affecting the formability of DSSs [5,6]. Another important reason that affects the alloy’s mechanical properties is columnar to equiaxed transition (CET) [7]. It often occurs during continuous casting solidification process and induces inhomogeneous mechanical properties and the microstructure varies with different processing parameters, such as pouring temperatures, cooling conditions (water flow rates in the cooling zones) and casting speed [8]."

Jan 1, 2012

By Merete Tangstad, Lars Klemet Jakobsson

"Slag refining is a promising refining method for boron removal from silicon as a part of a metallurgical route for production of silicon for solar cells. There is, however, limited data on the distribution of impurity elements between silicon and different types of slags. In the present study, the distribution of boron and calcium between silicon and slag were determined at 1600 °C for calcium silicate slags with a CaO/SiC>2 ratio between 0.65 and 1.3. An almost horizontal linear trend was found for the distribution of boron between silicon and slag, and the borate capacity was found to follow the relationln(CB0, ) = 30.8 + 2.96-V (1)where V\s the CaO/SiCh mass ratio within the range of the experiments.IntroductionSolar grade silicon feedstock contributes significantly to the total cost and energy required to make crystalline silicon solar cells. A less expensive and less energy requiring method of solar grade silicon production is therefore needed in order to make crystalline silicon solar cells more viable as an energy source. Silicon is an abundant element and the manufacturing cost of solar grade silicon is therefore mainly determined by costs related to purification of metallurgical grade silicon. The Siemens process is the most common process today, but it is an expensive and highly energy requiring process that gives silicon with a higher purity than is needed for crystalline silicon solar cells. A cheaper and less energy requiring method for production of solar grade silicon can either be achieved by modifying the Siemens process or by using a new production method. Purification of metallurgical grade silicon through a metallurgical route is a promising method that is already in use industrially. It has however proven to be hard to lower the boron content to 0.3 mg/kg or less, which is the requirement for most p-type crystalline silicon solar cell manufacturers. Slag refining is seen as one of the most promising approaches that can be used to bring down the boron content to the required level, but there is not much data on how boron is distributed between silicon and binary calcium silicate slags [1-4]. The distribution of boron between silicon and calcium silicate slags at 1600 °C has been studied in this work, and the obtained data has been used to calculate the borate capacity of binary calcium silicate slags."

Jan 1, 2012

By Lv Guozhi, Niu Liping, Liu Yan, Zhao Qiuyue, He Jicheng, Zhang Ting’an, Dou Zhihe

"This paper proposed a new method of Mg and Cl2 circulating for titanium sponge production by direct pyrolysis and thermal reduction process. Effects of pyrolysis temperature, pyrolysis time and partial pressure of oxygen on pyrolysis efficiency were researched, and the crystallite structural transformation of MgO productions at different pyrolysis temperature and time were analyzed by XRD. The experimental results indicates that the pyrolysis temperature and time effects the pyrolysis efficiency obviously, and the reasonable pyrolysis conditions by using MgCl2 in molten state are as follows: the pyrolysis temperature is 1100?, pyrolysis time is 60min and the partial pressure of oxygen is 100%, the pyrolysis efficiency get above 95% at this conditions. The dynamic analysis of molten magnesium chloride pyrolysis reaction shows that, as a chemical reaction process control, the response of the apparent activation energy Ea=70.4 kJ/mol.IntroductionTitanium is a young metal, it is applied in industrial until the Second World War. It is 160 years from the discovery of titanium to the industrial production of ductility titanium by magnesium reduction method in the United States in 1948. As a new kind of metal, titanium and titanium material are better than the traditional metal materials in mechanical properties, heat resistance and thermal conductivity. Titanium is a kind of landmark structure and function material, which is called “space metal”, “Marine metal”, “Intelligent metal” [1-3]. Although the study of new methods of titanium melting get more at present, Kroll method and Hunter method are really applied to industrial production methods for titanium smelting, and Hunter method is already discontinued because of costs at present. The core technology in Kroll method of sponge titanium production process can be ome down to two circulation, namely the cycle of magnesium and chlorine in preparation-process of titanium sponge. In the traditional Kroll method, the cycle is realized through magnesium chloride which is produced by the electrolytic magnesium reduction process in hot molten state. But because investment of equipment for electrolysis method is too high, this method has not been used by most titanium sponge production enterprise in China. At present most titanium sponge production enterprise in China produce titanium sponge by the outsourcing of titanium tetrachloride, but the main disadvantage of this method is that the by-product of magnesium chloride is difficult to deal with."

Jan 1, 2012

By Hao Deng, Hongmin Zhu, Jichao Li, Kai Huang

"Silicon and silicon carbide mixing micropowders obtained from the saw cutting industry of polycrystalline silicon ingot is separated by a simple sequential sedimentation. The Zeta potentials of the powders in the aqueous suspension are adjusted by varying the pHs with dilute acid or alkaline reagents. The dispersion and aggregation content of the microparticles is significantly influenced by pHs, and so their settlement velocity in the same hydraulic conditions are quite different, and silicon powders tend to suspend in the upper section of the suspension for its finer size and smaller density under the stronger Zeta potential repulsion force. The original content of the cutting powders with 30%wt silicon are separated into the Si-rich and SiC-rich powder respectively, and 62%wt Si-rich powder can be obtained after 4 times of sedimentation under pH = 8.0, showing the great potential for Si and SiC powder separation and recovery in a cost-effective way.IntroductionWith the fast development of photovoltaic (PV) technology these years, the market demand for the solar-grade high pure silicon material significantly increased, making the silicon recycling and recovery from the wire sawing slurry profitable and attractive[1]. Waste silicon slurry was produced in the multi-wire sawing process of a silicon ingot by using an ethylene glycol-based solution and silicon carbide abrasives as the slicing system. During this slicing process, about 30% of the silicon ingot will become the waste as the fine particles suspended in the slurry, which mainly consists of silicon kerf-loss particles, SiC fragmental particles, tiny iron fragments from the worn sawing wire and ethylene glycol-based solution [2]. The separation of above individual component is usually easy except for Si and SiC fine particles for their quite similar properties. So the biggest challenge for the effective recovery and recycling of silicon particles from the wire sawing slurry actually lies in the mutual separation of silicon and silicon carbide particles."

Jan 1, 2012

By Xinghua He, Shujing Zhu

"Cycled fluidized bed ash (CFBA), a significant portion of fly ash produced from coal-fired power plants and rejected from the ash classifying process, has remained unused due to its high free CaO and S03 content. It is necessary to extend research on the method to reduce the expansion and improve the compressive strength by some effective chemical activator. This paper presents experimental results on the expansion by Le chaterlier tester and the compressive strength. Hydraulic ash-zeolite (HAZ) cementitious material was blended as the chemical activator to study the effects of the activator on the expansion and the compressive strength. The results show that HAZ can not only reduce the expansion, but also increase the prisms compressive strength. Scanning electron microscope observation and X-ray diffraction analysis indicate that the main hydrated products of the sample are calcium hydroxide, ettringite, zeolite and calcite, which can explain the results of the expansion and the strength tests.IntroductionNearly 80% of the electricity in China is produced by coal-fired plants, which results in the production of a large quantity of coal combustion residues, among which coal fly ash is the major component. Because of that the air-pollution becomes heavier as time going on. Cycle-fluidized-bed-combustion systems are retrofitted to meet air-emission standards mandated by China Clean Air Act. Cycle fluidized bed ash (CFBA) will present new challenges for coal-combustion byproduct management. The use of cycle-fluidized-bed ash as a cement replacement in concrete is the most attractive one because of its high volume utilization and widespread construction. However, the replacement of cement with cycle fluidized bed ash in Portland cement concrete usually increases the expansion and decreases the early strength of concrete. In many research of this field, most of them were focus on the activation of pozzolanic activity of CFBA and to make all kinds of blend cement. A number of studies had been carried out on the activation of CFBA using chemical activators. These studies involved using different activating methods including alkali activation and sulfate activation 11, 2]. The former involved the breaking down of the glass phases in an elevated alkaline environment to accelerate the reaction [3, 4]. The later is based on the ability of sulfates to react with aluminum oxide in the glass phase of CFBA to produce ettringite that contributes to the strength at early ages [5-7]. With respect to sulfate activation, the use of gypsum and sodium sulfate had been well studied [5-8]. HAZ is one of HAS sub-products which is a patentd chemical activator made by Wuhan University (ZL98113594.3). It had been used to activate CFBA to produce blend cement in many Chinese engineering projects and time has told us that it is a good activator."

Jan 1, 2012

By Leijun Li, M. M. Mahapatra

"A three-dimensional finite element model with moving heat source was developed for pulsed-laser powder deposition (PLPD) process. Experiments were conducted to study the repair of superalloy components using the PLPD process. During the experiments, IN 625 powder was deposited on a superalloy substrate similar to IN 738. The process was modeled using three-dimensional finite element analysis. Element birth and death technique was used in the finite element model for simulating the deposition of powder layer on the substrate. A moving distributed heat source was used in the thermal model for realistic simulation of the process. Temperature dependent thermal material properties including enthalpy were used for the powder and the substrate in the transient thermal analyses. The fusion zones and peak temperature distributions of the deposits were predicted from the transient thermal analyses.IntroductionPoor weldability is a critical issue of superalloy repairing. The microstructural directionality of the superalloy components are disrupted when repaired by the fusion welding processes. Currently there is no widely accepted method to economically and reliably repair directionally solidified superalloys components. Pulsed laser powder deposition process (PLPD) is a promising repairing technique as the substrate is not severely affected by the heat source.In this study PLPD technology is used as the tool for superalloy repairing. In most of the land based turbine engines the directionally solidified nickel based superalloy similar to IN 738 [1] is used as the bucket material. The turbine engine blade tips are subjected to a combination of extreme operating conditions and corrosive environment. The tip of the nickel based turbine engine blades can be repaired using IN 625 material as suggested in the literature [1-2]. IN 625 is considered to be ductile and strong enough for the purpose of Ni based turbine engine blade tip repair[1-2]. During the present PLPD investigation, IN 625 powder was used as the deposit material on an experimental super alloy substrate similar to IN 738 superalloy used as the cast superalloy for the turbine engine blades."

Jan 1, 2012

By Ting Luo, Hongmin Zhu, Kai Huang, Shuanglong Du, Tao Gui, Yifan Xiu

"Poplar cotton, a cellulosic material, was found to adsorb metals ions effectively. In the present study, the biosorption characteristics of Pb(II) onto poplar cotton, were evaluated as a function of pH, contact time, biomass dosage, initial concentration and temperature. Within the pH range investigated (1.0-6.0), the optimal pH value suitable for the uptake of Pb(II) was determined. The maximum adsorption capacity obtained from the Langmuir model is around 0.52mol kg for the poplar cotton sorbent. Equilibration is achieved in 60min for the studied concentrations. Results suggest that the poplar cotton can be directly used as an effective and low-cost biosorbent for removal of Pb(II) from aqueous solution.IntroductionHigh value utilization of various biowastes produced in agricultural, forestry, fishing industries, etc. have attracted great interest from many researchers [1], Biomass, due to its easy availability, great abundance, low cost, easy processing, eco-friendliness and biodegradability, has exhibited exciting potential for being used as raw materials for the preparation of many new hi-tech functional products [2]. For example, using biowastes to synthesize sorbents for application in the removal of toxic substances such as dyes [3], heavy metals from the waste water [4] or in the recovery of valuable metals [5] from the ore tailings and secondary metals resources has made great progress in last decade. In present study, poplar cotton, a kind of white light fluff of poplar trees, like that of dandelion, usually flying in the air each spring was tested as a biosorbent for the remove lead ions from the water. It may also provide some good ideas for new sorbent design. Lead, as one of the typical poisonous heavy metals, for its typical toxicity and extensive pollution, was chosen to test the adsorption behavior of poplar cotton in aqueous solutions."

Jan 1, 2012

By Michael Heximer, Dominic Verfielst, Timothy Moore

"Teck's Trail Operations recently installed new pressure filters in the cold stage purification step in the zinc leaching plant. Alloy 2205 duplex stainless steel was chosen as the material of construction as it was in use in the hot stage purification operation. Within a year of commissioning, an unacceptably high rate (greater than 1 mm/y) of corrosion was observed on the weld heat affected zone (HAZ). Laboratory and field tests were conducted to establish the conditions under which the corrosion was occurring. The tests isolated the aggressive conditions to a unique combination of materials present during the filter regeneration stage. Furthermore, the change of the duplex grain structure of the alloy during welding resulted in the HAZ being more susceptible to the corrosive environment. A new material of construction was recommended as a result of the investigation.IntroductionThe sulphide leaching plant uses four horizontal tank pressure leaf filters to remove solids precipitated in the cold stage electrolyte purification process. The current filters were installed in 2007, and replaced a bank of filter presses. The material of construction for the filters - alloy 2205 duplex stainless steel - was selected based on its successful use in similar service areas of the leaching plant. However, within the first year, unexpected and rapid corrosion of the filter tank material was observed. Although moderate general corrosion was noted throughout the filters, the attack was particularly aggressive in the areas where intense heat was applied during fabrication, observed at the HAZs caused by welding, and on the exposed edge grain of the duplex plates. On the inaugural annual inspection of the filters in the first year of operation, a corrosion penetration rate of 1.0 to 1.5 mm/y was observed at the HAZs. The parent plate of the pressure tank was a minimum of 6 mm, with a minimum allowable thickness of 3 mm under the ASME pressure tank design rules. Therefore, the projected useful life of the filters could then be roughly calculated to be two to three years. Urgent action was required to understand and correct this problem."

Jan 1, 2012

By S. V. Ketov, V. P. Menushenkov, V. S. Shubakov

"The glass samples were obtained by melting of the oxides mixture SrO-Fe2O3-B2O3(Al2O3) at 1200-1250°C with subsequent quenching of the melt on quickly rotating steel roller. Submicronsized Sr(Fe,Al)12O19 particles were formed in glass-ceramic matrix during the crystallization aging of glass. The aging temperature Tag varied in the range 650-950°C. The submicron-sized hexaferrite powder was obtained by removing of the matrix phases using etching. The samples were characterized by X-ray diffraction, scamiing electron microscopy and magnetization measurements. The glass-ceramic material exhibits very high coercivity value up to 10 kOe. The samples of magnets were obtained by pressing of the hexaferrite powder at RT and subsequent aging in the range 900-1200°C. The aged samples exhibit coercivity value up to 8 kOe.IntroductionStrontium M-type hexaferrites have been widely used in technology and industry mainly for production of permanent magnets owing to their appropriate magnetic properties, chemical stability and low cost [1,2]. The SrFe12019-based compounds are characterized by high magnetocrystalline anisotropy and single easy magnetization axis. The highest coercivity is received for monodomain, defect-free single crystal particles with size D - 100 mn. Finely grained strontium hexaferrite prepared by chemical methods such as sol-gel pyrolysis and oxide glass crystallization exhibits high coercivity up to 6-8 kOe [3-5]. Owing to the partial substitution of Al for Fe in the strontium hexaferrite leading to the increase in the magnetic anisotropy field Ha=2Ki/M,, the increase in the coercivity may be received [6]. The notable results were achieved using the SrO-Fe2O3-AlzO3-B2O3 glass crystallization and formation of perfect submicron crystals of alumina-doped hexaferrite [ 6, 7]. The coercive force of glassceramics reached values of up to 10 kOe. Hexaferrite particles are well faceted and have the shape ofhexagonal bipyramids with truncated vertexes [7].In the present paper, we report results of our investigation into the SrO-Fe2O3-B2O3(Al2O3) glass crystallization, hexaferrite powders and permanent magnets, which were prepared by pressing submicron-sized hexaferrite powders at RT and subsequent sintering at 900-1200°C."

Jan 1, 2012

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 Bradford C. Wesstrom, Omar Araujo

"Impurities from an electrolytic refinery are typically extracted from the electrolyte utilizing conventional electrowinning cells. These cells are arranged in series with cascading solution flow and are commonly referred to as liberator cells. The Freeport McMoRan Copper & Gold El Paso Refinery has optimized the removal of arsenic in cascading liberator cells by utilizing two separate feed solutions. The primary feed solution is recycled liberator electrolyte and the secondary feed solution is ""neat"" tank house electrolyte. The secondary feed solution is added based on the voltage response across the individual cells utilizing independent variable frequency drive (VFD) pumps. When the voltage across a cell changes, a signal is sent to the VFD pump to maintain a cell voltage of 1.98 volts. By maintaining this voltage the copper content in each cell exits at 2-4 grams per liter. This safely optimizes the arsenic removal as copper arsenides on the liberator cathodes.IntroductionDuring the electrolytic refining of copper, impurities from the copper anode report both to the bottom of the electrolytic refining cell as slimes and to the electrolyte. The impurities which enter the electrolyte are arsenic, antimony, bismuth and nickel. The impurities that report to the electrolyte during the electrolysis process gradually increase. As these impurities increase, they are incorporated into the refined copper cathode. There are many processes that have been used to remove these impurities from refinery electrolytes. Some of them are listed as follows: solvent extraction, ion exchange, hydrogen sulfide reduction, bioreactor, adsorption onto a low - solubility metal-oxide hydrate, adsorption onto activated carbon and EMEW cells. The conventional process used by the copper refining industry for controlling the level of impurities in electrolyte involves multistage electrolytic cascading liberator cells. In these cascading liberator cells copper, arsenic, antimony and bismuth are removed as various mixed deposits from the electrolyte. Removal of these impurities is achieved through an increase in voltage resulting from the depletion of copper in the electrolyte through electrowinning. With this higher voltage, the Group Vb elements, arsenic, antimony and bismuth are deposited on the copper cathode and report as slimes to the bottom of the cells. Nickel is removed in a subsequent process."

Jan 1, 2012

By Naiyang Ma

"High oil concentration is one of the major barriers for recycling of mill scale of steel hot rolling mills. It is of vital importance to find cost-effective technologies of reducing oil concentration in mill scale in order to recycle the mill scale without causing detrimental effects on production and environment. This paper discusses in-process separation of mill scale from oil at steel hot rolling mills. Formation of mill scale and status of oily wastewater at hot rolling mills are reviewed in the first place. A mathematical model is then formulated to relate oil concentration in mill scale to physical properties of mill scale, chemical and physical properties of wastewater and interacting parameters between mill scale particles and wastewater. From this model, three approaches of in-process separation of mill scale from oil are derived: (1) avoiding contacts between mill scale particles and oily wastewater, and (2) maintaining low oil concentration in wastewater, and (3) collecting mill scale in upper streams of wastewater flows. In-process separation of mill scale from oil might have advantages of lower capital cost, lower operating cost and less additional environmental concerns, compared to other strategies of separating mill scale from oil.IntroductionHot rolling is an inevitable step in producing finished steel products. Figure 1 schematically shows a steel hot rolling process. Semi-finished steel products, slabs here, are reheated first, and then the reheated slabs are discharged from the furnaces and transported on hot rolling trains to descaling units for removing scale with pressurized water. After being descaled, the slabs are rolled by roughing mills. After treated with cropping and the second descaling, the slabs are finally rolled into finished products, coils here, by finishing mills."

Jan 1, 2012

By Klaus Gamweger

"This paper introduces an innovative solution to open and close the tap hole of different furnace types in the copper industry with a slide gate system. Two plates with defined drilled holes are slid against each other, which enables effective starting and stopping of the copper flow as well as throttling. Typically, the copper is poured via a tap hole into a launder system by rotating the furnace into an appropriate position. Control of the casting rate is also performed in this manner. Or, in case of stationary furnaces the tap hole is opened by oxygen lancing and closed manually with a clay- or copper-cone. These procedures show a lot of disadvantages including splashing, oxygen pick-up, and energy losses as well as a severe danger for the working staff. All these problems can be overcome with an appropriate slide gate system.IntroductionThe control of the casting rate of a copper anode furnace usually is performed by rotating the furnace into an appropriate position. This implies that the taping starts with the tap hole at a very high position. Copper splashing and an uncontrolled oxygen pick up are - with several more disadvantages - the consequences. RHI AG has developed an innovative solution for copper applications to open and close the tap hole with a slide gate system which allows also an accurate control of the flow rate. By using this system it is possible to start the casting procedure with the tap hole at the deepest position, directly above the launder. This paper presents this new slide gate system in detail and shows the advantages in production and safety issues."

Jan 1, 2012

By Alejandro R. Alonso, Lizet Alvarado, Gretchen T. Lapidus

"Cobalt and lithium recovery from spent Li-ion secondary batteries has been increasingly studied in recent years due to the high value of both metals and the low proven reserves for lithium. The standard method employed until now has been the deactivation and crushing of the batteries, followed by leaching of the L1C0O2 spinel from the battery cathode using acid solutions, such as 1.5 to 2.0 M HC1 or H2SO4, in a temperature range from 120°C to 250°C. Once leached, the cobalt is separated by electrodeposition and the lithium by precipitation, using large amounts of carbonate to bring the solution to alkaline pH values. In the present work, citric-thiosulfate solutions are used for the spinel leach at room temperature, favoring a reductive environment at room temperature, which stabilizes the cobalt(II) as cobalt citrate and lithium(I) at pH 5, and recovers approximately 99% of both metals.IntroductionThe Li-ion batteries industry has become an important economic sector in recent years. This type of battery is the most promising system for energy storage, because of its high efficiency in charge-discharge cycles, and its adaptability to many configurations. The demand will probably increase because of the need for mobile energy sources in many types of devices ranging from cell phones, tablets, and laptops to medical, navigation and sophisticated communication equipment and even in automobiles.One major problem related to the use of these batteries is the method employed for recycling the components, mostly cobalt and lithium. Currently, there are two processes employed on an industrial scale: the Sony/Sumimoto process, used since 1990 [1] and the Toxco Process [2]. In the first case, incineration is used to open the batteries and at same time volatilize the organic solvents. After that, the metals (copper, iron and aluminum) are physically separated. The cobalt and lithium are recovered as oxides and then thermally treated in order to recycle them for new batteries manufacture."

Jan 1, 2012

By Takahiko Okura, Satoshi Okano, Hiromichi Takebe

"Fine zinc concentrates tend to become sticky when roasted in a fluidized-bed reactor. The oxidation of high-purity ZnS powders and ZnS concentrates with different particle sizes were studied in terms of phase changes and particle morphologies. The sample materials were directly oxidized to ZnO in a roasting process performed over 700°C. Zinc oxide particles with diameters less than 0.5 ìðé formed at 700°C; the particle size increased by grain growth at 900°C. The coarse ZnS concentrate formed the oxysulfate ZnO2ZnS04 when roasted at 700°C; the sulfate transformed to ZnO at higher temperature.1. IntroductionRoasting is an important step in zinc extractive metallurgy because more than 80% of the world's zinc is produced from zinc sulfide concentrates using the roast-leach-electrowinning [1,2]. Currently, zinc concentrates with a finer particle size distribution are used to enhance recovery rate. However, the finer zinc concentrates tend to produce a sticky calcine in a fluidized-bed roaster [3].The factors that affect products in a fluidized-bed roaster include particle size, contaminant, O2 and SO2 partial pressures, and the feeding method of ore to the roaster. This study examined roasting behavior of high-purity ZnS powders and ZnS concentrates with different particle sizes. The phase changes and particle morphologies of the calcine samples producted from theZnS powders were studied."

Jan 1, 2012

By Anand Kumar, Pradeep kumar Jha, Suman Kant, Pradeep Kumar

"It has been a major challenge to reduce the intermixed grade formation during ladle change-over operation in continuous casting process of tundish steelmaking. The F-curve generated by step input of the tracer (new grade steel) tells about the intermixed grade amount for different grade specifications. Use of flow modifiers is beneficial in reducing the intermixed grade because of the change in slope (in different time zones) and position of the F-curve due to their placement at tundish bottom. Present study aims at investigating the role of dam placed before the outlet in a multi-strand tundish with reference to the slope behavior of F-curve in different time zones during the teeming operation plays an important role in determining the intermixed amount.Introduction In Continuous casting process, the old grade steel remaining in the tundish (reservoir between ladle and mould) from the old ladle gets mixed with new grade steel from new ladle and leads to intermixed grade which is considered to be of inferior quality. Although formation of intermixed grade is inevitable with the sequential method of casting, its amount can be controlled by changing the flow behavior of steel inside the steel. Intermixing in a slab caster tundish was simulated using 3-D numerical model based on k-å turbulence equation and compared their result with that of water model experiment Yeh and Hwang [1]. Huang and Thomas [2] reported that quantity of residual fluid in tundish affects the composition distribution in the transitional slab and thus the intermixed length. Huang and Thomas [3] developed three sub models to predict mixing in tundish, liquid core of strand and solidification. Thomas [4] developed a one dimensional model to simulate the final composition distributions in slab caster of continuous casting and investigated the effect of process variables on the intermixing. Alizadeh mehdi et al., [5] simulated of the intermixing phenomenon for slab casting for three different sub models. Goldschmidt et al. [6] developed a numerical model that predicted the location of the intermixed steel in a four line round caster. Lan and Khodadadi [7] studied for the transient fluid flow of liquid steel, heat transfer and solidification during the flying tundish change process. Cho and Kim [8] developed a mixing model to predict the outlet concentration of the tundish during grade transition. Most of the work reported in the literature has dealt with intermixing in slab caster tundish. Billet caster units are more often being used by steel industries due to growing demand of billets. The multiple outlets lead to varying degree of intermixing with time owing to their different distance (location) from the inlet. Use of flow modifier to minimize the intermixed amount, however has also not been discussed in detail so far. Further no work has been reported regarding effect of slope of F-curves obtained through different outlets on intermixing. Hence keeping these objectives in mind attempt has been made by authors to analyze the slope of Fcurves after dividing them into three different time zones and the effect of these time zones on intermixing."

Jan 1, 2012

By Björn Hinzel, Joachim Rösler

"The most important characteristic of open-pored metals is porosity, since it enables all of their functional applications as filters or sound absorbers. Due to the notch effect of the pores, mechanical properties of porous metals are better than the ones of comparable structures made of polymers or ceramics. Consequently, only open-pored metals can be used in aircrafts to reduce flow noise or noise resulting from the core engine by acoustic absorption. Absorption properties depend highly on pore size and porosity of the material, which must be characterized as precisely as possible in order to analyze the correlation between morphology and noise reduction performance. Here, a line segmenting method is explained in order to characterize pore size and porosity of absorber materials using image processing based on two dimensional microscopy images, including sample preparation and specification of the set-up. Then, the influence of the pore structure on the measured absorption behavior is discussed. Finally, the correlation of acoustic behavior, pore morphology, and porosity is outlined.IntroductionSignificant noise loads affect everyone causing anxiety, depression, insomnia and other effects which impair health and productivity [1],[2]. Due to the rising number of flights and aircrafts, air traffic noise increases dramatically. To counter this development, various approaches have been developed to reduce the different noise sources resulting from airframe, jet or engine [3],[4],[5],[6]. One approach to reduce this noise is the application of noise reducing liners in the hot gas path [7]. This is especially important, since the engine is becoming the dominant noise source of modern airplanes during take-off [8]. Due to the elevated temperatures and high fatigue loading in this part of the aero-engine, conventional passive absorber materials cannot be used. Polymers would not be able to bear the heat and ceramic fibers would crack under the mechanical loading due to the notch effect. Consequently, this study focuses on metals with open pores, which can resist elevated temperatures and fatigue loading and additionally resemble geometrically conventional passive absorbers. Based on the production processes, e.g. sintering of metal fibers [7], powder processing using a foaming agent [9], coating of polymer foams [10], or using melt infiltration techniques [11], the characteristic dimension of the porosity is usually in the range of 0.01-10mm. In this work, sintered metals and metal sponges are analyzed after the theory of sound absorption is briefly outlined. Then, measurements of the acoustic absorption of metal sponges and sintered metals in an impedance tube are performed. To understand and predict the acoustic properties of metals with open porosity, it is necessary to characterize the materials as precisely as possible. This is explained in detail using a line segmenting technique, followed by a discussion of the connection of pore characteristics and acoustic absorption. Finally, a conclusion is given."

Jan 1, 2012