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By F. R. A. Jorgenson

The ignition of chalcopyrite and pyrite was studied using laminar flow furnace and thermal analysis techniques which were supported by XRD and optical microscopic examination of the products. In air, chalcopyrite and pyrite ignited at temperatures of 400-500'C and 500-600?C respectively. The phase assemblages predicted from thermodynamic analyses were compared with those found by experiment, and the onset of ignition was correlated against changes in the phase compositions. Pyrite and chalcopyrite ignited when pyrrhotite and intermediate solid solution formed thus opening up the structure and allowing ready access of oxygen.

Jan 1, 1989

By C. Takano

The integrated iron and steelmaking industry generates large amounts and many types of solid dusts and sludge, at different phases of the production. Within these are: sludge of the Blast Furnace; coke fines; fine and coarse fractions from oxygen converters; sludge from water treatment at rolling mill unit; and others. In this paper the above dusts and sludge were physically and chemically characterized. The obtained results allowed defining self-reducing pellets using these materials. The high temperature behavior of the pellets were evaluated. Good results, with no decrepitation and swelling, and high yield of reduction, show that it is feasible to recycle them, as self-reducing pellets, in oxygen steelmaking converter.

Jan 1, 2001

By Ma Ying

The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transfonnation under the condition of continuous casting by heated mold was studied. The mechanism of surface defects appearing in ZA alloy line was discussed and the structure of some defects were analyzed by SEM. The results show that only when the fitting of various technique factors, pressure head, outlet temperature, pulling speed and cooling condition are reasonable under a certain range, can the ZA alloy smooth line be continuously pulled out. Unreasonable techniques will result in hot tear, rough surface, mush outlet, leaking and other defects. The shape and location of solid-liquid zone have an important influence on the formation of the above defects. When the solid-liquid zone is located in the mould outlet or inner mould, the surface of solidification will protrude into the inner mould. If the remaining liquid cannot counteract the solidification contraction, a rough surface will appear. If the solidification surface further into the mould, the ingot in the mould will have a great friction force when pulling and will form a hot tear. When the solid-liquid zone is moved out of mould, the solidification surface will turn into a plane, which easily results in leaking. A vibration or unstable operation will cause an ingot winding during pulling.

Jan 1, 2003

By Merete Tangstad, Gabriella Tranell, Jeff Kline

"Raman spectroscopy as an instrumental technique for the determination of silicate structure is widely accepted. This method was utilized for analysis of structural modifications associated with the addition of network modifying species. Silicate melts are described by the extent of oxygen bridging. Therefore, understanding the effect different oxides have on modifying the silicate structure will provide valuable information regarding the removal of boron from silicon in slag refining processes. Samples ranging from CaO/SiO2 = 0.56-1.2 were evaluated with and without varying concentrations of B2O3. The addition of CaO to SiO2 revealed Q2 species constitute 45% of the Qn species and addition of B2O3 to the high concentration CaO system results in an increase in Q2 and a decrease in Q0 . The disappearance of the Raman band associated to the three-member ring in the low concentrated CaO system indicates boron addition and destruction of the ring.IntroductionExtensive studies on the structure of silicate systems have been performed using Raman spectroscopy with consensus on the Raman shift associated with different bridging oxygen units [1]. Most of these studies are motivated by the lack of a fundamental understanding of the processes involved in petrology. Due to this, an opportunity exists to build on the knowledge obtained from these studies and conduct more research on slag structures relevant to industrial applications, as these systems are often compositionally similar to magmatic melts. Raman spectroscopic studies of industrial slags will provide insight into the possible structural modifications necessary to enhance removal of impurity species from the metal phase to the slag phase."

Jan 1, 2012

By Carlos Mauricio Fontes Vieira, Sergio Neves Monteiro, Thiago Samarão Motta

This work has as its objective to characterize ceramic bodies formulated with ornamental rock waste and two different clays to produce ceramic paver. Specimens were made by uniaxial press-molding at 20 MPa and then fired at 950 and 1050oC respectively. The determined technological properties were: plasticity, dry bulk density, linear shrinkage, water absorption and flexural rupture strength. The results showed that the type of the clay has strong influence on the properties of interest for heavy clay ceramics. The investigated waste must be incorporated in small amounts to avoid increasing in the porosity of the ceramics.

Jan 1, 2015

By Y. K. Rao

Relatively pure crystalline lead sulfate (PbSO4) can be produced by chemical vapor transport from an impure source such as the lead-acid battery paste or the roast-ore-leach-residue from a hy¬drometallurgical process-route. In a closed-reactor, transport of matter is induced by a tempera¬ture-gradient and the steady-state transfer rate can be calculated using the data on the standard free energies of formation for the species present and the pertinent binary diffusion coefficients. The present work focusses on chemical vapor transport in a tubular reactor (1.4-cm inner diameter x 10-cm long) with the source- and deposition-ends held at 850°C (T,) and 750°C (Td), respectively; PbC12(g) is the 'solvent' or 'transport agent' and NiSO4(s) placed in the source-zone -serves to maintain a sufficiently high S0,-potential such that the stability of the lead sulfate species is ensured. For the purposes of analysis, the gas-phase in the reactor is assumed to consist of eight species: H2O, PbC12, SO3, SO2. O2 HO, C12, and PbC14. The reaction between C12(g) and PbSO4(s) in the high-temperature source-zone produces PbCl2, SO2, and 02; four more reaction-equilibria in the same zone yield other species. In the low-temperature deposition-zone, reaction equilibrium involving PbC12, H2O, and SO, leads to the nucleation and growth of PbSO4 crystals; three other reaction-equilibria occur in this zone. By employing the virtual equilibrium state for the end-zones and coupling it to the Stefan-Maxwell diffusion equations for each of the gas species, the respective partial pressures for these, in the source- and deposition-zones, are computed at steady-state. From these data, the molar fluxes of PbCl2. PbCl4, and so forth, are determined. Allowing for the transport-enhancing effects of thermal convection, the net transport rate of lead (or PbSO4) is duly calculated for specified initial conditions. The predicted rates show very good agreement with measured rate data reported in the literature [ V. Plies, T. Kohlmann and R. Gruehn: Z. anorg. allg. Chem, 568, 62 (1989)

Jan 1, 1995

By O. Forsén

A new cell construction was designed for the study of the electrochemical behaviour of additives in conditions that simulate real copper, electrorefining. The behaviour of gelatine and thiourea was studied by applying different electrochemical methods, i.e. polarization resistance and voltametric measurements. In this study, individual galvanostatic electrolysis experiments were carried out for 120 hours. The organic additives were introduced to the electrolyte at certain intervals and their concentration was varied in the range &om zero to four ppm. An optical microscope was applied for the examination of copper cathode deposit microstructures. The results show that gelatine has a polarizing effect on the deposition potential of copper whereas even small amounts of thiourea depolarize the electrodeposition of copper. The maximum inhibitor efficiency of gelatine was obtained at a gelatine concentration of slightly lower than two ppm. When both gelatine and thiourea were present in the electrolyte, the depolarizing effect of thiourea exceeded completely the polarizing effect of gelatine. If chloride ions were added to gelatine and thiourea containing electrolyte, the electrochemical behaviour of the system was altered drastically. Chloride ions resulted in the prevailing of polarization effect caused by gelatine while the depolarizing effect of thiourea disappeared in this system. The polarizing effect of gelatine increased until chloride ion concentration of 30 ppm was reached. Also, the above electrochemical phenomena could be detected in the optical examination of copper deposit microstructure.

Jan 1, 1995

By R. Padilla

A thermogravimetric study has been conducted to follow the decomposition and volatilization of arsenic from enargite concentrate in nitrogen and slightly oxidizing atmospheres. Temperature has a large effect on the rate of volatilization of arsenic. Fractional volatilization of arsenic as high as 98% were obtained in less than 60 min at 650°C in nitrogen atmosphere, while in slightly oxidizing atmosphere the same volatilization could be achieved in 30 min. It was found that arsenic volatilizes as sulfide in nitrogen atmosphere and as 4xture of sulfide and oxide in atmospheres containing 1% oxygen. By using the pore blocking and the first order kinetic models, apparent activation energies of 213 and 200 kJ/mol for the temperature range of 780 - 900 K and 205 and 184 kJ/mol for the temperature range of 900 - 985 K were determined for enargite and copper concentrate, respectively.

Jan 1, 1997

By Hans Jürgen Maier, Gregory Gerstein, Florian Nürnberger

Microstructural analysis to support the development of material models provides valuable information to design complex forming operations. Damage models such as e.g. by Gurson consider spherical voids only. However, investigations of bcc steels by scanning electron microscopy reveal that voids exhibit an ellipsoidal shape with progressing deformation. The material’s weakening in the Gurson model is taken into account by the void volume fraction. Therefore, a three-dimensional characterization of the void shape offers important data for modelling. Thus, information on the anisotropy of the process of void evolution and accordingly, about the anisotropy of the deformation process is provided. Application of the information regarding the void shape anisotropy within the Gurson model is discussed.

Jan 1, 2016

By Jorge A. S. Tenorio, Chuanwei Zhuo, Joner O. Alves, Yiannis A. Levendis

"The ever increasing number of automobiles and the consequential increase in consumption of tires have generated a pressing environmental issue, concerning the disposal of unserviceable tires. The worldwide disposed of waste tires is approximately 1 billion units per year and this amount is expected to increase by 2% each year. This work presents a microstructural characterization of nanomaterials synthesized in a catalyst system from the effluent of burning waste tire chips in a horizontal two-stage laminar-flow furnace. Controlled combustion of waste tire chips took place at temperatures of 900 or 1000 °C, and stainless steel meshes were used to synthesize the nanomaterials at 1000°C. Produced materials were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalyst meshes were covered by materials with diameters of 20 to 200 nm and lengths of about 40 µm. They possessed structures similar to those of carbon nanotubes.IntroductionThe motor vehicles on the road have been increasing annually. World motor vehicle production in 2009 approached 62 million units. Consequently, the consumption of tires has also been on the rise; about 1.4 billion units were produced around the world in 2007 [l]. The disposal of scrap tires is a serious environmental problem. The worldwide disposed of waste tires is almost 1 billion units per year with an expected increase of around 2% each year. However, less than 7% of produced waste tires are recycled (excluding reuse, retreading or incineration). The waste rubber tires are a thermoset polymer, which cannot be reprocessed like thermoplastics polymers, therefore the recycling of this material requires special techniques that demand big investments [2, 3].A solution to the disposal of waste tires is the sequential pyrolysis/combustion process. Past research showed that waste tires are an attractive potential fuel due the high heating value (29-3 7 MJ/kg), which is comparable, or even higher to those of typical bituminous coals [ 4, 5]. Pyrolysis is a process wherein the material is thermally decomposed at elevated temperatures at the absence of an oxidizing gas. Combustion is characterized by the addition of the oxidizing gases during the process. Several studies indicate that the pyrolysis and combustion processes for the tires treatment have a great energy conversion potential [4, 5, 6]."

Jan 1, 2011

By Jim Sundal

Primary steel manufacturers using electric arc furnaces generate one of the largest hazardous waste streams nationwide. The waste stream, known as electric arc furnace dust, is a listed hazardous waste with the designation K061. Oregon Steel Mills, Inc., (OSM) of Portland, Oregon, has implemented a process known as Glassificationn, which uses KO61 as an ingredient in an onsite recycling process. Because OSM was able to demonstrate that the Glassificationm recycling process beneficially uses all toxic constituents in the electric arc furnace dust and that the recycling process produces marketable products, the process is not subject to Resource Conservation and Recovery Act (RCRA) permit requirements. The marketable products manufactured using Glassificationn include roofing granules, ceramic glazes and colorants, abrasive blasting media and, more recently, synthetic slag fluidizers. The purpose of this paper is to identify the regulatory issues for recycling hazardous waste and demonstrate that OSM glass frit is effective as a slag fluidizer in primary steel manufacturing.

Jan 1, 1994

By Zhou Shu-cai

"A method has been proposed for the pre-treatment of high phosphorus iron ore by carbothermic reduction assisted with microwave irradiation and magnetic separation on a laboratory scale. Chemical analysis of the reduced ore sample, the metal sample and the slag sample were conducted. Based on the above research, the influences of carbon addition, microwave power and microwave irradiation time on the recovery of Fe and dephosphorization were discussed. It indicated that the increase of microwave irradiation time and power had substantial effect on the recovery of Fe while the influence of carbon addition was not obvious and the highest iron recovery ratio reaches some 95.5% when the dephosphorization ratio was 37.68%. A high iron recovery ratio and a reasonable dephosphorization rate were incompatible under the conditions investigated in this study due to the reduced iron and because unreduced P-contained gangues were not efficiently separated. This method may provide a reference for the future utilisation of high-phosphorus iron ore.IntroductionWith the rapid growth of crude steel production in China, the source of iron ore tends to become increasingly strained and is facing the risks of raw material shortage for the iron and steel industry. In order to decrease the production cost, China has to focus on the utilization of its domestic low grade iron ores for the iron and steel plants [1-2]. China has a large deposit of high phosphorous iron ore with a reserve of 7.45 billion tons which is unused in any large scale [3]. Therefore, the development of a successful and economically viable technology for high phosphorus iron ore is of profound importance. To remove phosphorus from the high phosphorus iron ore, several mineral and metallurgical processes have been proposed, such as bio-leaching [4], roasting reduction plus melting separation [5], pre-reduction and screening methods combined with mechanical crushing or air jet milling[6] selective agglomeration plus reverse flotation [7]. However these processes are not cost effective or are time consuming. The traditional pyrometallurgical process( BF+ BOF) refuse this kind of ore mainly because that molten iron is saturated with carbon or high carbon content and thus all phosphor us in the burden goes to the molten iron[8]. Therefore, it is important to exploit the cheap and abundant high phosphorus iron ore as a resource in ironmaking. In recent years, the microwave was widely introduced as a heat resource for extractive metallurgy of iron ore or other minerals. For example, microwave assisted ore milling, microwave assisted carbothermic reduction of metal oxides and microwave assisted mineral leaching issues[9-10]"

Jan 1, 2014

By Miguel N. Herrera

The electrochemistry of coal pyrite is relevant to coal desulfurization by chemical or bacterial leaching, flotation and oil agglomeration. The electrochemical behavior of polished and etched Upper Freeport and Pittsburgh coal pyrite samples was investigated from pH 1.0 to 10.5. The open-circuit potentials decreased with increasing pH, as expected, but were well above the thermodynamic stability region of pyrite, and decreased with time. Cyclic voltammetry revealed behavior highly sensitive to pH and scan rate (2.0 and 20.0 mV/s). The behavior on the first cycle was always substantially different from that on subsequent cycles. The anodic and cathodic reactions were correlated with the Eh-pH diagram for the Fe-S-H20 system to identify the reactions occurring at different pH values. There was also evidence that the buffers used to maintain basic pH values are themselves electrochemically active, which should be considered in interpreting many earlier electrochemical studies of sulfide minerals.

Jan 1, 1994

By S. Neogy, M. Gupta, D. Srivastava, V. Kain, S. Roychowdhury, R. C. Prasad, G. K. Dey

"Austenitic stainless steels are an important material of construction for Boiling Water Reactors (BWR). These stainless steels are amenable to strengthening by strain hardening. Various deformation modes at different test temperatures and strain become active. In the present investigation type 304LN stainless steel was used in the annealed and strain hardened condition. Thin foils were prepared from gauge section for transmission electron microscope (TEM) investigation after tensile testing at room temperature and at 288°C. TEM investigation reveals that twinning is the major mode of deformation for the tests done at room temperature while dislocation cross-slip is the major mode of deformation at higher temperature. Stacking faults were also observed to a limited extent. The extent of twinning was much higher for the tests done using the rolled material. The formation of martensite in the stainless steel due to straining was investigated by the analysis of selected area diffraction patterns.IntroductionAustenitic stainless steels (type 300 series) are an important material of construction in Boiling Water Reactors (BWR). These stainless steels cannot be heat treated but can be strengthened by cold working [1]. Nitrogen alloying of these stainless steels result in high strain hardening rates and higher strength without any loss in toughness [1]. Stress Corrosion Cracking (SCC) in BWR of these types of stainless steels have been attributed to surface strain hardening and strain hardening ofregions adjacent to constrained weldment [2].The test temperature [3, 4], prestrain [5] and nitrogen level [5] has been reported to affect the deformation mechanism during tensile testing. Byun et al. [3] have reported the formation of martensite, dislocations, stacking faults and twinning during tensile deformation, the extent of each depending on the test temperature. Strain localisation has been reported to occur during tensile deformation in irradiated stainless steels [ 6]. The behaviour of rolled material during tensile testing is similar to that of irradiated material to a large extent [3]. Austenitic stainless steels are low stacking fault energy (SFE) materials in which various types of microstructures have been reported to form during tensile deformation and the strain is also highly heterogeneous in nature in these stainless steels which aides SCC in BWR environment to a large extent [7]. During cold working of austenitic stainless steels second order twinning has also been reported [8]. Knowledge about the deformation mechanisms operative in the strain hardened austenitic stainless steels during tensile testing at different temperatures is essential to understand the material deformation behavior and the present study aims at enhancing the existing understanding."

Jan 1, 2011

By Christoph Sagadin

Corrosion mechanisms between high melting synthetic ferronickel slags and refractory were investigated. The used slags were prepared by mixing and melting of specific oxides. Substrates of the applied refractory material and specimens of FeNi slags were heated in a hot stage microscope up to 1650 °C. The experiments were performed under a defined gas atmosphere of 60% CO and 40% CO2. A further examination of the formed phases between slag and refractory occurred by scanning electron microscope. The investigations indicate that the slag penetrates between magnesia grains and partly dissolves magnesia. Spot analyses show that iron diffuses into the magnesia grains, which transform to magnesiawustite, meanwhile SiO2 forms different types of olivine like forsterite and monticellite. Thermodynamic calculations confirm the formation of these phases. The combination of practical lab scale experiments and thermodynamic calculations should finally contribute to an improvement of the refractory lifetime and performance.

By Lucas Barbosa de Souza Martins, Felipe Perissé Duarte Lopes, Nathalia Carneiro Garcia Rosa, Lucas Lopes da Costa, Sergio Neves Monteiro, Rubén Jesus Sanchez Rodriguez

"The fibers extracted from the stem of the banana plant are relatively stronger and have been used as reinforcement of polymer matrix composites. In addition to quasi-static mechanical properties, there is a need to characterize the dynamic behavior of banana fiber composites subjected to thermal and mechanical constraints. In this work, the temperature variation of the dynamicmechanical parameters of polyester composites incorporated with up 30% in volume of banana fibers were investigated by DMA tests. The storage and loss moduli as well as the tangent delta were measured from 20 to 200°C in a TA Instrument operated with the flexural mode at 1 Hz. The results showed that the incorporation of banana fibers tends to increase the viscoelastic stiffness of the polyester matrix. It was also observed changes in the T g and the structure dumping capacity of the composites with increasing fraction of banana fibers.IntroductionNatural fibers with high amount of cellulose, also known as lignocellulosic fibers, have been used from primeval times by our civilization. In the last century, synthetic fibers such as nylon, carbon, aramid and glass fibers gained interest owing to superior strength and precise dimensional control. Natural fibers were then replaced by synthetics in many fields such as textiles and appliances. In the past decades, however, environmental issues drawn, once again, the attention to lignocellulosic fibers as possible substitute for intensive energy-consuming and long term polluting synthetics, specially the glass fiber [1]. In particular, research works have disclosed the potential advantages associated with the use of lignocellulosic fibers as the reinforcing phase in polymer composites [2-7]. Among the advantages it is worth mentioning the renewability, recyclability, biodegradability and the fact that natural fibers are neutral with respect to C02 emissions responsible for global warming. Moreover, as compared to synthetics, lignocellulosic fibers present lower density and cost as well as reduced wear caused to the processing equipment. On the other hand, in terms of composite reinforcement, hydrophilic lignocellulosic fibers present drawbacks such as weak adhesion to hydrophobic polymeric matrices in addition to dimensional limitations and non-uniform properties."

Jan 1, 2011

By Ilija Ilic

Recovery of tin from tinplate and production of good-quality detinned-plate for further processing in ironworks has been the subject of interest for many years. Tinplates are mostly used for production of tin containers for food industry and consumer goods. The research carried out so far included determination of the parameters of dissolution of tin from tinplates by alkaline solution of NaOH and electrochemical recovery of tin from the alkaline solutions. During leaching, NaNO3 and methanitrobenzoic acid (MNBA) as oxidants were studied. By leaching the waste tinplate which contains 0.31 % of tin with a solution of 1.12 mol/dm3 NaOH, 0.26 mol/dm3 Na2CO3 and 0.09 mol/dm3 MNBA at temperature of 70°C for 60 mm, a degree of tin leaching of 97 % was attained. MNBA facilitates oxidation of Sn2+ into Sn4+ suitable for obtaining compact, and not spongy, Sn cathode deposit, as it was the ease earlier. Recovery of tin by electrolysis from solutions obtained by leaching was studied to determine the effect of electrolyte composition on the quality of cathode deposit and the degree of electric current efficiency. Experimental results obtained at a laboratory level were checked on an enlarged laboratory set up where continuos leaching of tin from waste tinplate and its electrolytic recovery from the solution obtained were carried out. The experimental set-up -operated under semi-industrial conditions, and about 500 kg of waste tinplate was processed yielding about 1.160 kg of tin (99 % Sn).

Jan 1, 2000

By Satu Jyrkönen

A single-particle laminar-flow technique was used to study reactions of sulfidic nickel particles. The studied materials were three natural nickel concentrates and four synthesised nickel mattes. The variables of the experiments were the gas preheating temperature (500 - 1300°C), the composition of the reaction gas (N2 + 0 - 75 vol-% 02) and the ,particle size of the feed. Chemical analysis of the particles was used to determine the oxidation degree of the materials, and optical and scanning electron microscopy were used to detect alteration in their morphology, internal composition and structure. General reactivity of the materials was monitored by the extent of sulfur removal. The reaction mechanism of the studied materials was found to depend primarily on the materials composition as well as oxygen content of the reaction gas.

Jan 1, 1998

Numerical simulation of the fluid flow and heat transfer has been carried out for a waste-heat boiler in an Outokumpu type copper flash smelter. In this boiler, SO2-containing off-gas flows into the waste-heat boiler radiation section at about 1350°C. A fraction of cooler off-gas from the electrostatic precipitator at about 200°C was recirculated into the radiation section, and a small amount of ambient air was leaked into the boiler from the bottom. The computational results show that the flow is strongly recirculating and distinctly three dimensional in most of the boiler, particularly in the radiation section. The hot off-gas cooled down rapidly after entering the radiation section due to radiation. The predicted flow pattern and temperature distribution were in a good agreement with laboratory models and industrial measurements.

Jan 1, 1995

By James R. Craig

The General Image Processing System (GIPSY) is being employed for the quantitative textural analysis of complex sulfide ores from the Southern and Central Appalachians and for the determination of liberation characteristics of the mineral constituents during grinding. Optical images from a microscope-mounted TV camera or from 35mm film are converted into digital images which are subsequently analyzed by GIPSY, a transportable image processing software package. Properties measured by GIPSY include spatial distribution of mineral constituents, grain sizes, grain shapes, grain orientation and mineral co-occurrences.

Jan 1, 1982