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By Leonardo Mota, Felipe Perissé Duarte Lopes, Marcelo Gomes da Silva, Sergio Neves Monteiro, Helion Vargas

"Natural fibers, as a class of material, are attracting the interest of engineering sectors owing to specific advantages such as comparatively reduced cost and lower density as well as environmental benefits associated with renewability and biodegradability. For industrial applications, thermal properties, among others, are required. These are major requirements, especially in the case of an insulating natural fiber. In the present work, thermal properties of the curaua were investigated by photothermal techniques, i.e., the open photoacoustic cell and a method based upon the monitoring of the temperature evolution as a function of time. This investigation, in tum, permitted to evaluate two important thermal properties: the thermal diffusivity and the specific heat capacity of the curaua fibers. Indirectly, by means of simple mathematical relations, the thermal conductivity was also obtained. The results were compared with other materials and characterize the curaua fiber as an efficient insulator.IntroductionMaterials are gaining attention in recent years owing to their benefits for the environment as compared to synthetics. Being biodegradable, yearly renewable and recyclable, the natural planted-based are considered fully sustainable [1]. In particular, their life-cycle, from growing to industrial processing, absorbs as much C02 as it is emitted and makes them neutral with respect to greenhouse gases responsible for global warming [2]. Typical examples of these environmentfriendly materials are the lignocellulosic fibers that have been used in simple items such as ropes, baskets, textile, modest roofing, etc, since the beginning of our civilization [3]. In the past few decades, these natural fibers have been extensively investigated [ 4-1 O] as a possible reinforcement phase of polymer composites in substitution for synthetic fibers. In fact, engineering application of lignocellulosic composites are today in the market, especially in the automobile industry [11-13]. Out of the hundreds available natural fibers, only part of them exhibits superior properties to be qualified for composite reinforcement."

Jan 1, 2011

By Olga Slavkina

A new technology of bacterial leaching by means of the Thiobacillus ferrooxidance bacteria is proposed. The equations of reactions that describe of the first and the second stage of bacterial leaching of sulfide raw materials containing non-ferrous metals are given. The theory is analyzed and the technology of processing of some complicated substandard concentrate containing copper and zinc is proposed. The main technological operations including a two-stage bacterial leaching and stages of copper and zinc recovery in the form of marketable product are described. The results of the experimental validation of the main technological parameters of the first stage are given. The main possibilities of a more complete zinc and copper recovery at the second stage of bacterial leaching are discussed in comparison with single-stage leaching process.

Jan 1, 2003

By Vince Newberry

Alcan Rolled Products at Oswego, New York, commissioned Recycle II during May of 1995. Recycle II is an advanced technology UBC recycling facility designed to meet the most stringent environmental standards enforced to date in the United States, particularly with respect to NO, and particulate emissions. This paper addresses the exacting requirements and strategies of Alcan's Recycle II project andThorpe Technologies' design considerations and solutions for the supply of environmentally favorable melting furnace and delacquering systems. The furnaces are equipped with low NOx regenerative burners and furnace pressure and hearth gas flow controls designed specifically for processing the hearth gases through baghouses. The delacquering system is a new generation Apros concurrent flow unit designed for low NOx emissions.

Jan 1, 1995

By Jean Goldschmidt

Recycling of fine oxidized particles of non-ferrous metals usually cannot be carried out by pyrometallurgical methods. 'Hydrometallurgy provides an alternative technology to reintroduce? the resulting products as secondary raw materials into the industrial cycle, thereby saving resources and energy while keeping the environment a little cleaner. The paper summarizes the methods employed by Hydrometal to achieve these objectives and? stigmatizes the latest counterproductive international regulations which create ever more obstacles to environmentally sound recycling.

Jan 1, 1995

By Yuanbo Zhang, Mingjun Rao, Guanghui Li, Chongzhong Ouyang, Shuhui Zhang

Oolitic hematite ore with high-phosphorus content is currently recognized as one of the most refractory iron ore resources in the world. The high-phosphorus content and unique structure of the oolitic hematite ore make it difficult to be beneficiated. The process of direct reduction followed by magnetic separation has significance to the utilization of oolitic hematite ore, and sodium salts can improve the dephosphorization. However, the behavior of phosphorus during reduction roasting, and the intensified dephosphorization mechanism of sodium salts are not clear. In this study, by using chemical analysis, chemical phase analysis, XRD analysis, optical microscopy, and scanning electron microscopy analyses, the behavior of phosphorus during reduction roasting of high-phosphorus content oolitic hematite ore and the effect of sodium salts on behavior of phosphorus were studied.

Jan 1, 2015

By B. Q. Li, R. A. Mirshams

"A numerical algorithm is described for the simultaneous prediction of the thermomechanical behavior of the materials and microstructure evolption during metal forging. The numerical development is based on the finite element solution of the thermoviscoplastic deformation of metals coupled with the internal state variable model describing the microstructure evolution involving work hardening, recovery, recrystallization and grain size distribution. The finite element code for rigid viscoplastic deformation is developed based on the modification of the existing code for the thermal and fluid flow calculations. The code is tested against and compares well with the results reported in literature. The procedures for the integration of the · rnicrostructure model into the macro finite element model are described. Results are presented showing the characteristics of materials dynamics and mechanical deformation during simple metal forging processes.IntroductionIn industrial deformation processes such as hot rolling and forging, the workpiece undergoes both macroscopic plastic deformations and microstructural evolution. A computer model that allows to predict both materials dynamics and macroscopic deformation is obviously more useful for both fundamental understanding and deformation process optimization. For some industrial applications, especially those involving novel, light and high strength materials, such an integrated model is critical in that both materials and thermomechanical 'behavior during forging must be carefully controlled to obtain the products that meet the desired strength requirement [I]."

Jan 1, 2000

By Junji Shibata

Zeolite synthesized from coal fly ash has many intelligent properties such as cation exchange, adsorption, catalyst and so on. The suitable use of the zeolite, however, is not established in an actual commercial scale yet. From the viewpoints of an effective usage of coal fly ash and the zeolite obtained from coal fly ash, we propose the new concept for environmentally friendly usage of zeolite, in which coal fly ash safely returns to the soil with growing plants and purifying wastewater. This method can make great contribution to recycle of coal fly ash, to purification of high nutritious water and to tree planting.

Jan 1, 2002

By Xiping Chen, Wangxing Li

"Spent potlining is unavoidable solid waste from aluminum smelters. About thirty kilograms spent potlining is discharged in China to produce per ton primary aluminum. Spent potlining has high level soluble fluorides and cyanides so that it brings heavy pollution to environment. It is prohibited to keep a large amount of spent potlining in open air because it will lead concentrated pollution to local soil and water source due to hydrated reactions between spent potlining and rain water/moisture in air. Landfill may solve pollution of spent potlining provisionally, but it is difficult to be accepted by aluminum smelters because of its high investment, troublesome monitoring and perennial maintenance. Detoxifying of spent potlining not only can remove deleterious fluorides and cyanides in SPL, but also can make fluorides in SPL recycle and return to aluminum electrolysis cells, at the same time benign SPL solid residue can be recycled and ready for cement production.IntroductionChina became the largest primary aluminum manufacturer in 2001. In the past few years, its aluminum output increased by twentyfive percent every year and reached 12.56 million metric tons in 2007. The whole world was very surprised and focused attention upon Chinese aluminum industry. It is more and more important to keep sustainable and steady development with the rapid development of Chinese economy. Aluminum industry is an important base industry and does a great contribution to Chinese economy. But aluminum industry is high energy-consumption and heavy-pollution industry. The government has paid more attention to aluminum industry in recent years. Nowadays the bothersome problem which counterworks Chinese aluminum industry is pollution from solid wastes. Main Solid wastes from aluminum industry are red mud from alumina refineries and spent potlining (short as SPL) from aluminum smelters. Spent potlining are waste lining materials from aluminum electrolysis cells. During production of aluminum, due to reactions between melted electrolyzer and pot lining as well as penetrating of fluorides into pot lining, newly-formed compounds inlayed in pot lining, destroyed the lining structure and brought pot lining cracking. Melt rushed out of lining cracks, cells have to be stopped running and ready for heavy repair. Cell life generally varies from 1500 to 2000 days. Spent potling is an unavoidable solid waste from aluminum industry."

Jan 1, 2008

By Xu-ling Chen, Qian Li, Yong-bin Yang, Zhao Jing, Tao Jiang, Guang-hui Li

"It is generally known that alkali metals are harmful to blast furnace production resulting in aggravating RDI of sinters, abnormal expansion of pellets, deteriorating blast furnace lining, etc. Sinters regarded as dominating burden of blast furnace are determined as the main source of alkali metals. In this study, the removal behavior of potassium and sodium oxides by pre-reduction sintering during the sintering process was studied. The removal ratio ofK20 and Na20 was greatly influenced by coke powder content, carbon species, coke powder adding ways, additive and so on. Under the conditions of carbon rate 12% and 5% dosage of CO supplied in the sintering process, the corresponding removal ratio ofK20, Na20 was 69.00% and 32.79%, and metallization ratio could reach 4.65%. This technology provided a novel process for reducing the content of alkali metals in sinters and dramatically improving the quality of blast furnace burden.IntroductionSinter is the main iron-bearing charge of blast furnace for iron-making in China, making up about 80% of the total burden; therefore, its quality has a significant influence on the quality of pig iron and blast furnace operation. Research and practice of numerous years prove that potassium and sodium coming from ores are brought into blast furnace and upgraded, which is one of the essential reasons that lead to blast furnace nodulation and influences its strength. Currently, effective flow sheet to remove potassium and sodium is weak magnetic separation-intensive magnetic separation-flotation [l], while iron ore concentrate is still ofhigh levels of potassium and sodium. As sintering process is also not effective to remove potassium and sodium, blast furnace in China is of high alkali burden, e.g. it reaches 5.6-6.2kg/tFe in Baotou iron making plant, which is greater than international tolerated level of2.55kgltFe [l]."

Jan 1, 2013

By Vinicius Alves Gomes, Jean Igor Margem, Thallis Cordeiro, Frederico Muylaert Margem, Roberto Faria Jr., Sergio Neves Monteiro, Marina Rangel Margem

Natural fibers are attracting the interest of engineering sectors owing to specific advantages such as lightweight and lower cost as well as for their inherent condition of being renewable, biodegradable, recyclable and neutral with respect to CO2 emission. In particular, the fiber extracted from the malva plant stem is nowadays recognized as one of the strongest lignocellulosic fibers. However, the thermal properties of the malva fibers have yet not been fully investigated. The present work had as its objective to investigate, by photoacoustic spectroscopy and photothermal techniques the thermal properties of diffusivity, specific heat capacity and conductivity of a pressed malva fibers sample. The results revealed that these fibers showed a superior thermal insulation capacity.

Jan 1, 2015

By Mostafa O. El-Bealy

"To estimate the interdendritic cracking tendency in casting processes, a new model for interdendritic cracking criteria has been proposed. The model combines a concept of the alloying element effect on the interdendritic strain generation and therefore on the susceptibility of interdendritic cracking phenomena. A susceptibility of interdendritic cracking is modeled by using El-Bealy's interdendritic cracking susceptibility function ""BJCSF' and the opening displacement between the dendrites ""EIA "". These concepts are modeled based on the previous experimental observations and ElBealy' approach. The model is implemented numerically for a one-dimensional model problem with some similarities to the casting of steel. The variation of some key parameters that are known to influence the frequency and severity of the interdendritic cracking is then studied.I. INTRODUCTIONInterdendritic cracking ""hot tearing"" commonly encountered in both ferrous and nonferrous castings (1,2]. It is generally believed that interdendritic cracks start to nucleate and develop in the interdendritic strain region within the mushy zone [l-5]. The interdendritic strain region is then definitely coherent, but continuous films of liquid still exit (4,5]. This distinguishes interdendritic cracks from cold cracks forming during the casting process after complete solidification (6,7].Much effort has been put into the understanding of the interdendritic cracking phenomena, and several theories have been proposed. Fellini [8] stated that interdendritic crack ""hot tear"" will result if the material is subjected to too high of accumulated strain within so called vulnerable part of the solidification interval. Kinosita et. al. [9] and Campbell (10] also emphasized the role of tensile stresses in the forming of interdendritic cracks. Most interdendritic cracks criteria simply consider the size of solidification interval, stating that solidification range is associated with a lager interdendritic cracking susceptibility than a short range. Clyne and Davies (11] formulated a more refined such criteria based upon the time spent in different regimes of the solidification interval. They defined a vulnerable region in which thin continuous films of interdendritic liquid exist, and the permeability is low. When thermal strains are induced in this region, the film is not able to sustain the stresses, and an interdendritic crack will form."

Jan 1, 2001

By K. C. Mills, P. N. Quested, A. P. Day, R. F. Brooks

"Methods have been developed to measure the physical properties of molten materials relevant to the fluid flow in high temperature processes. Data for the densities, viscosities and surface tensions of Al-, Ni- and Fe-based alloys are compared with (i) values for the pure metals and (ii) estimated values obtained from models making use of chemical composition of the alloy. Experimental values for metallurgical slags are also given and compared with estimated values.1 IntroductionPhysical property data has proved very useful in improving process control and product quality. For instance, in the continuous casting of steel the viscosity (TJ) of the mould flux is important since it determines (i) the optimum casting conditions, nVc = 2.5±1 dPas (m min-1) where V c is the casting speed and (ii) the level of slag entrapment (which leads to inclusions) in the metal. Thus data for properties like viscosity are exceedingly useful in understanding the process and the problems encountered and the causes of defects and problems.Another interesting development which has helped to increase our knowledge of processes and improve process control and product quality is the development of mathematical models of the fluid and heat flow in the process. These models have been developed to the stage where one of the prime requirements is for good physical property data for the industrial materials involved. Recently, Oxley [1] has shown that the use of reliable, experimental, property values for the commercial alloy in a commercial software package produced a significant improvement in the prediction of casting defects. Thus reliable property data are required for liquid metals but also for (i) liquid slags since many processes involve the use of a slag to refine and protect the metal or to lubricate the mould and (ii) refractories, sand and investment moulds."

Jan 1, 1999

By G. T. Lapidus, O. J. Solis-Marcial

"The oxidative dissolution of copper from refractory minerals, such as chalcopynte, represents a technological challenge that has occupied hydrometallurgists for more than half a century. Innumerable processes have been suggested, but the majority operates at high temperatures or employs corrosive media. The origin of this refractory nature is the formation of passivating phases of iron(III) or copper. One option is to add non-corrosive ligands that complex these metal ions, thereby facilitating their dissolution. In the present work, the effect of acetone in sulfuric acid solutions was studied. The initial experiments were on chalcopynte carbon paste electrodes using cyclic voltammetry, where greater reactivity was observed. Later, leaching tests with hydrogen peroxide, cupric sulfate and ozone and, as oxidants, were performed. High extractions were achieved in three hours at 50°C. The solid residues contained the iron in the form of Fe203 and FeOOH.IntroductionChalcopyrite is the most important mineral of polysulfide copper ores [1] and accounts for approximately 70% of the world's copper reserves [2]. Currently, the copper present in chalcopyrite is extracted mainly by pyrometallurgical processes, which generate environmental concerns because of the formation of SO2 gas and submicron particulates [3]. The development of a less aggressive hydrometallurgical process for the extraction of copper would constitute a possible solution to these problems. For that reason, studies of the dissolution behavior of chalcopyrite are of great technological importance [4], However, the proposed oxidative leaching routes for chalcopyrite, generally at high pressures and temperatures, have not been implemented on an industrial scale, because of the elevated costs required to equal the high copper extractions obtained in thermal processes. These extreme leaching conditions are required because of the refractory nature of chalcopyrite. Passivation has been used to explain this phenomenon, although researchers have disagreed on the composition of the layer, which is various have assumed to be sulfur, copper sulfides, and iron-bearing jarosites or hydroxides [5]. If the latter compounds are the cause, an alternative solution would be the use of polar organic solvents in the oxidative leach to decrease the formation of the passivating iron layer. In this work, the influence of acetone on the oxidative leaching of a chalcopyrite concentrate at room conditions is explored."

Jan 1, 2012

By C. Y. Tang, Z. H. Chen, T. C. Lee

"In sheet metal forming process, the forming limit and strain distribution are governed by plastic instability and fracture following strain localization. It has been proved that the temperature gradient caused by plastic deformation as well as friction is one of the crucial factors to induce the strain localization in high-speed metal forming processes. In this paper, a numerical simulation of the sheet metal extrusion process has been conducted by using thermal-mechanical coupling finite element method. An improved mixed finite element method has been used to solve the large deformation elasto-plastic problem. In thermal phase, the transient heat transfer finite element method together with the Crank-Nicholson algorithm has been employed to determine the temperature field. Both the numerical results and the experimental observations reveal that the temperature gradient plays an important role in inducing the strain localization, which eventually leads to fracture failure in the sheet metal extrusion process.IntroductionSheet metal extrusion is such a process where the extrusion punch penetrates into one surface of the sheet metal material to let it extrude and flow towards the outlet of the die. This process can be used to produce protruding parts on a strip material. In engineering applications, the quality of the product is affected by many factors such as stress state, loading speed, material properties and lubrication condition. The research on failure mechanisms and improvement of formability in sheet metal forming processes by exploitation of differential thermal conditions has been of great interest recently [1-3]. It has been proved that the temperature gradient caused by plastic deformation, heat transfer, and friction between sheet and tools is one of crucial factors to affect 'the formability in high speed sheet metal forming processes [4]. In our previous study of sheet metal extrusion, it has been observed that plastic deformation is highly localized and some specimens are subjected to fracture failure in the form of crack propagation [5]. To understand this failure phenomenon, the effects of temperature gradients must not be ignored."

Jan 1, 2001

By P. Myllykoski, J. Nylander, A. S. Korhonen, J. Larkiola

The coefficient of friction and the deformation resistance have been determined from the measured rolling parameters by applying the Bland-Ford-Ellis rolling force model and the artificial neural network model (ANN). The dependence of friction on the parameters such as reduction, rolling speed, front and back tensions, contact pressure and deformation resistance have been studied by the ANN model. Measured data of over 10 000 coils have been used in the training stage. Various dependencies have been examined and the results show that the friction coefficient does not depend much on the rolling speed. The reduction and deformation resistance seem to have the strongest effect on the friction coefficient. A friction model based on neural computing has been included into the existing rolling force model.

Jan 1, 1994

By Wenjun Duan, Qingbo Yu, Qin Qin, Junxiang Liu

In the study, the coke-oven gas (COG)-steam reforming process using hot blast furnace slag (BFS) as the heat carrier is explored for producing hydrogen and recovering high-grade waste heat of hot BFS. The method of the Gibbs energy minimization approach through Lagrange multiplier is adopted in the thermodynamic analysis of reforming process. The simulation is carried out to study the operation pressure, temperature and steam to carbon ratio (S/C) based on the chemical equilibrium calculations. The optimal operation conditions are determined to improve the yield and fraction of hydrogen in the COG-steam reforming process. The results suggest that the preferential operation conditions for COG-steam reforming process to produce hydrogen are achieved at 600ºC, 1.5MPa and S/C (5.0). Due to the CaO and other melts in BFS, CH4, CO and CO2 in COG are converted and removed efficiently, especially CO2. The hydrogen fraction reaches to 86.7% and its production is about 1.22mol with 1mol of the COG.

Jan 1, 2016

By Frederico Muylaert Margem, Giulio Rodrigues Altoé, Glenio Daniel, Pedro Amoy Netto, Sergio Neves Monteiro, Maria Carolina Andrade Teles

The environmental concern is creating pressure for the substitution of high energy consumption materials for natural and sustainable ones. Compared to synthetic fibers, natural fibers have shown advantages in technical aspects such as flexibility and toughness. So there is a growing worldwide interest in the use of these fibers. Fique fiber extracted from fique plant, presents some significant characteristic, but until now only few studies on fique fiber were performed. This work aims to make the analysis of the tensile strength of polyester composites reinforced with fique fibers. The fibers were incorporated into the polyester matrix with volume fraction from 0 to 30%. After fracture the specimens were analyzed by a SEM (scanning electron microscope).

Jan 1, 2015

By Takao Yasugi

The majority of copper in the raw material migrates to the de-copperized dross that forms when the crude lead produced in the blast furnace is treated in the de-copperizing process. The de-copperized dross is treated in the electric furnace producing matte, speiss, and crude lead. The de-copperized dross also contains the silver. Therefore, it is important to improve the rate of silver migration to the crude lead. For this reason, the behavior of silver between the matte, speiss and crude lead phases was examined. At the same time, several tests to improve the percentage of silver migrating to crude lead were conducted.

Jan 1, 2003

By Sung-Mo Jung

Experiments were carried out on a system with artificially prepared slags in a graphite crucible, in order to examine the possibility of recycling BOF slags produced in the steelmaking process. More than 80% of FeO and P2O5 was reduced within 20 minutes and the FeO reduction rate was greater than that of P2O5. P2O5 reduction began after more than 60% of FeO was reduced. Increasing slag basicity enhanced the reduction of FeO and P2O5. Temperature also improved slag reduction. The overall reduction rate was controlled by the chemical reaction at the slag/carbon interface. The reduction rates of FeO and P2O5 were second and first order with respect to their respective contents. Most of the reduced phosphorous is believed to vaporize in the form of P2 gas.

Jan 1, 2006

By Dilek Kirgöz, Onuralp Yücel, Murat Alkan

"In this study, Mo containing Fe-based alloys, such as Fe-Ni-Cr-Mo, were synthesized using a mixture of Fe203-NiO-Cr203-Mo03 powders reducing with Al powders by metallothermic process which is a high energy efficient, fast and low-cost production technique for synthesis of cast alloys and advanced ceramics. Detailed thermochemical studies were simulated by using FactSage 6.2 Thermochemical software in order to calculate adiabatic temperature of the reactions and effects of initial molar composition on the final products. In the metallothermic processes, effects of stoichiometric Al addition and addition of the oxide powders (Alz03, Si02, CaO, MgO) on the metal recovery and compositions of final alloys were carried out. Final products were characterized by using chemical analysis (AAS), XRD, XRF and SEM/EDS techniques.IntroductionSelf Propagating High Temperature Synthesis (SHS) has significant advantages compared to the high technology furnace applications, such as very short processing time, simple operation, low energy requirement and low cost [l, 2]. In a SHS process, the ignition starts the combustion and propagates throughout the reactant mixture yielding the desired product. However, the disadvantages of the process such as inhomogeneous or unreacted products due to undesirable reaction rates needs to be overcome by changing some parameters such as ignition temperature, particle size, additive, atmosphere etc. [3, 4]. This work aims to establish a scientific and engineering background in the production of some cast Fe based alloys (Fe-Ni-Cr-Mo) which are used as surface coatings, wear-corrosion-oxidation resistive applications via SHS (Self Propagating High Temperature Synthesis) metallurgy which is attractive process technique regarding fast and low-cost production ability of cast alloys."

Jan 1, 2013