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By Jussi Vaamol

A commercial CFD-code was used to solve isothermal flow fields of gas and liquid in a Peirce-Smith converter. The model was validated with a 1/4 scale water model, and parametric study. Limits of the modeling technique used were recognized, but calculated results indicate that the present model predicts the general flow field with reasonable accuracy. The model was used to examine general flow conditions in an industrial scale PS-converter. Typical scaling factors of physical models were also evaluated with the aid of predicted bubble distribution, patterns of the flow fields and magnitude of flow velocities. The numerical simulations were found to open new viewpoints to the fluid dynamic related phenomena in the PS-process.

Jan 1, 1998

By Courtney A. Young

Cyanide is a critically important chemical to the mining and metallurgical industry. It has a strong affinity for metals making it favorable as an agent for metal finishing and treatment as well as a lixiviant for metal leaching, particularly gold. These technologies are environmentally sound but, because cyanide is very toxic, safeguards are required to prevent accidental spills and treat effluents before being discharged. Various methods of cyanide remediation by separation and destruction for cyanide management purposes are therefore reviewed. The methods have been broadly categorized as physical, -adsorption. complexation and oxidation methods including photolysis and other advanced-oxidation processes. Reaction mechanisms for these methods are presented throughout this paper, Finally, the methods are compared in regards to their effectiveness in treating various cyanide species: free cyanide, thiocyanate, weak-acid dissociables, and strong-acid dissociables.

Jan 1, 1998

By Antonio de Lucas, Juan Francisco Rodríguez, Ignacio Gracia, Mª Teresa García

"The amount of waste of Polystyrene (PS) foams is increasing in last years due to their use in insulation, protecting and, storing many different food products. Conventional methods of recycling such as crushing and shrinking by heated air or frictional heat have the disadvantages of molecular degradation, resulting in a reduction of the quality of the recycled polymer. Dissolution and shrinking with suitable solvents is one of the cheapest and more efficient ways of polystyrene recycling but in the process of the solvent recovery by distillation a certain degree of molecular degradation is produced. In this way, CO2 supercritical technology appears as an interesting alternative for the elimination of solvent. This work proposes a global process to polystyrene recycling in two steps: a polystyrene dissolution with a suitable “green” solvent followed by its elimination by supercritical tecnologhy. In order to develop a “green process” the constituents of essential oils, limonene, terpinene, cymene, and phellandrene, are selected as the most appropriated solvents. Introduction In the last years, disposal of the non-biodegradable plastic wastes has been recognized as a serious environmental problem. Recycling these wastes has great interest in order to prevent the environmental pollution and to preserve natural sources (1, 2, 3). Since the Polystyrene foams (PS) is one of the most used foam in isolation, protecting and food storage most of recycling work is concerned with this polyolefin (4). The two main alternatives for treating polymer wastes are energy recycling, where wastes are incinerated, and mechanical recycling (5). Environmental argumentations such as toxic emissions are building up a public resistance against incineration process (6). Mechanical recycling is a popular recovery path for manufacturers and is carried out on single-polymer waste streams. Any way, the market for recycled products can only be found if the quality is close to that of the original. Unfortunately the process of classification and further recovery of these wastes makes them often more expensive than virgin plastic (7, 8). Solvent extraction is one of the cheapest and more efficient ways for PS recycling. If it is done in house of waste producers the separation between plastics could be easy and effective and the transport costs would be eliminated."

Jan 1, 2008

By Kazue Moriya

At the 1980 TMS-AIME world symposium, Dr. Davey mentioned that the traditional lead blast furnace is now being challenged by direct smelting processes. In the copper smelting field both the blast furnace and reverberatory furnace are also disappearing in favour of direct smelting processes such as Outokumpu flash smelting, Mitsubishi continuous smelting, Noranda furnace, Inco furnace and so on. Those new processes all have the following in common: (1) High degree of mechanization (2) Metallurgical reactions carried out in closed vessels (3) Application of oxygen and/or oxygen enriched air (4) Minimization of handling materials and gaseous volume (5) Minimum energy requirements (6) Removal of workers from near the furnace (7) Reduction of emissions of harmful gas to meet environmental regulations. (8) Improvement to the work place environment to avoid occupational hygiene hazards. Direct and continuous smelting of powdered concentrate in one vessel was a romance of the metallurgist since early times. However as mentioned above, in the copper field this objective is being achieved in practice. The industry however can't deny that the serious and severe regulation of environmental pollution in every country was the prime motive for the modernization of smelters. In early days, to meet regulations, it was anticipated that many economic difficulties such as higher capital and energy costs and extravagant use of resources and waste disposal would be the result. "Turn a misfortune into a blessing" is an old saying which reveals the current thinking and reacent developments in the nonferrous industries. In the last ten years in the lead smelting field, about two decades later than copper, commercial scale smelting using new furnance technology has started. The KIVCET process and QSL process, which is flash smelting and bath smelting respectively, are becoming major competitors. They will be sure to upgrade their processes to remain economically and environmentally viable in the comming decade.

Jan 1, 1990

By Youliang He

Twin-roll casting is an integrated casting and rolling process that involves the continuous solidification of a melt and the plastic deformation of the solidified metal between two rotating rolls. Computer modeling is a valuable tool to help engineers understand the metallurgical process during twin-roll casting. However, commercially available software can only model either the fluid flow/heat transfer of the melt or the plastic deformation of the solid, but not both. In this study, an object-oriented finite element program was developed to simulate the steady-state fluid flow, solidification and plastic deformation of an A7,31 magnesium alloy in a horizontal twin-roll caster. The melt, the mush zone and the solid were treated as a generalized Newtonian flow in an Eulerian reference frame and different constitutive equations were employed to describe the material behaviours. The effect of operational parameters on the solidification process was discussed based on the simulation results.

Jan 1, 2010

By Arthur W. Cooper

This paper contains a review of the development of blast furnace? slag handling and processing technology in the Ironmaking industry over the past 30 years, with an emphasis on economic and environmental factors. The requirements and practice of air-cooling slag for use as aggregate and of pelletizing and granulating slag for use in cement manufacture are described. The operation of slag pits, slag pots or ladles, the slag pelletizer and early granulation systems are compared with the new continuous .granulation, dewatering and handling systems developed in the past decade.

Jan 1, 1992

By Toshiyuki Kawai

Copper concentrate smelting directly in P-S converters was started at Onahama Smelter in 1983. Thereafter, the tonnage of concentrate smelted through the P-S converters increased, such that by 2002, it equaled the tonnage smelted through the reverberatory furnaces. In 2003, 56% of the total copper concentrates treated at Onahama Smelter were processed directly through the P-S converters. Technical improvements are reviewed and advantages of direct smelting in P-S converters are reported.

Jan 1, 2005

By Germán Richter a

To comply with the chilean air quality regulation requirements, the Hernan Videla Lira Smelter which is a custom smelter having to cope with a wide variety of concentrates, has developed a two-step modernization plan. The main steps are: - A second acid plant of 80,000 Nm3/hr to be operating at the end of 1996. This will increase the sulphur capture from 43% to 701/o in association with the replacement of the Hoboken converter by a second PS-converter to reduce the operation problems resulting from the treating of high garde matte. - Oxygen enrichment, is going to be incorporated in 1998 in the Teniente Converter and PS-converters in association with tuyere injection of dry concentrates, increasing the sulphur capture to 90 - 93% of sulphur inputs. By this program, sulphur emissions will be decreased from 40,000 tpy today to less than 8,000 tpy and in this way to carry out the environmental regulations.

Jan 1, 1996

By Payman Roonasi

Having knowledge of mechanism of magnetite formation is essential in a number of industrial processes including magnetite synthesis and corrosion of iron. In this study, magnetite nanoparticle was synthesized via two different ways; coprecipitation of iron (II) and (III) and oxidation of ferrous hydroxide. The samples were characterized using X-ray diffraction (XRD), Mid-Far IR spectroscopy, scanning electron microscopy (SEM), chemical analysis for determination of Fe II/Fe III ratio and ICP-MS for iron isotopic ratio (56Fe/54Fe) measurement. Since fractionation of iron isotopes depends on reaction rate and bonding strength, interpretation of the isotopic data with respect to the possible mechanisms is discussed. No fractionation of iron isotopes was observed for the magnetite synthesized by coprecipitation, whilst magnetite formed from ferrous hydroxide showed higher abundance of 54Fe compared to 56Fe in the beginning of reaction, implying the significance of the following reaction:

Jan 1, 2009

By Mishark Nnabuchi

A heterojunction of PbS - CuS thin film has been grown on glass slides by SGT. The films were annealed for 1hr at temperature of 373K and 423K respectively. The optical properties were characterized using a UNICO UV - 2102 PC Spectrophotometer at normal incidence of light in the wavelength range of 200 - 1000nm. The minimum percentage transmittance was observed to be 34% for sample A and 25% for sample B within the same optical region. The band gap energy was determined from the spectra to be 2.05eV for sample A and 1.85eV for sample B which gave a band shift of 0.20eV. It can thus be concluded that the optical properties of the films within the VIS - UV - NIR can find application in solar thermal technology, particularly as antireflection coating, window materials and as good materials for selective solar cell fabrication.

Jan 1, 2010

By Andres Vikdahl

The Rönnsktär smelter has recently undergone a series of technical and operational changes. This changes are caused by our own will to remain and gain in competivety and to adapt to the ever changing surroundings. To be able to remain competitive in surrounding with high wage costs, high inflation and high environmental standards thorough cost management is needed. The Swedish economic policy in the beginning of the 80'ies consisted amongst other things of two devaluations. The exchange rate of the Swedish Krona was reduced with approximatively 25 %. This boosted the profits of our export industry, some even believed we entered the land of milk and honey ... And working in this promised land where everything turns into profit it is very difficult to be careful and restrictive with your spendings. Apart from some healthy and fruitful investments we allowed ourselves yearly steady increases in salary for ever reduced number of worked hours and we of course employed more people. Inflation rates went up and so did property prices. In 1986 finally reality catched up on us. Reality in the form of too high costs started to hit Swedish export industry 5-6 years after the big devaluations. Furthermore the high inflation rate also hit the domestic industry a couple of years later. Together with other important factors Sweden faced a severe home-made recession in the beginning of the 90'ies. With this background we now report and analyse our smelter's performance and operating results, shown in fig 1 The main constrictions on smelting and refining at Rönnsktär are today: * Income restrictions by governmental production level Limit * Throughput resmctions by governmental emission limit * High capital costs in the aftermath of Swedish high inflation in the recent decade * Low work force turnover Below we will illustrate how we tackled with these issues along the following lines: * People * Quality * Technology

Jan 1, 1993

By F. Kavicka

An original application of ANSYS simulated the forming of the temperature field of a massive casting from ductile cast-iron during the application various methods of its cooling using chills. The numerical model managed to optimize more than one method of cooling but, in addition to that, provided serious results for the successive model of structural and chemical heterogeneity, and so it also contributes to influencing the pouring structure. The file containing the acquired results from both models brings new and, simultaneously, remarkable findings of causal relationships between the structural and chemical heterogeneity and the local solidification time in any point of the casting. The determined relations therefore enable the prediction of the face density of the spheroids of graphite in dependence on the local solidification time. The calculated temperature field of 500x500x1000 mm casting of ductile cast-iron with various methods of cooling has successfully been compared with temperatures obtained experimentally. Acknowledgments. This analysis was conducted using a program devised within the framework of the GA CR projects (No.106/04/1334, No. 106/04/1006 and No. 106/04/094), of the COSTAPOMAT-OC526.10, MPO/FI-IM/021, EUREKA No.2716 COOP and KONTAKT 14/ 2005/06.

Jan 1, 2006

By A. González

Arsenic is one of the main contaminants present in Chilean copper concentrates and its abatement represents a challenge for the process metallurgy, particularly under the strong environmental requirements in the global community. The possibility to form ferric arsenate directly from a gas phase by means of a heterogeneous reaction between an arsenic gas bearing and iron oxide was studied at laboratory scale. A thermodynamical analysis for the system Fe-As-O-S has been initially made, in order to obtain the stability conditions for the ferric arsenate or other FeAsyO2 type compounds. Experiments were made using an hematite sample suspended in a thermogravimetric device. AS4O6 gas generated from solid AS2O3 that was passed through the iron oxide sample and its instantaneous weight change was recorded directly. A kinetic study for the AS4O6 volatilization was made to control the gas composition. A chemical control between 300 and 600°C with an apparent activation energy of around 14 Kcal/mol As2O3 was determined. The samples after the reactions were chemically and XRD analysed. Arsenates detected corresponds to complex compounds. Results shows a dependence on temperature and oxygen content in the gas phase. The kinetics for iron arsenates formation is slow, reaching an arsenic capture of 6% after 80 minutes of reaction when an oxygen content of 50% is fed continuously at 800°C and 3,56% As in the gas. Experiences made at the same temperature but under higher oxygen content in a closed reactor, allowed arsenic capture close to 60%. For higher temperatures the capture is considerably lower.

Jan 1, 2003

By Pengfu Tan

Electric arc furnace (EAF) dust from the steel industries is listed by the United Sates EPA as a hazardous waste under the regulations of the Resource Conservation and Recovery Act due to the presence of lead, cadmium and chromium. The disposal of the approximately 650,000 tons of EAF dust per year in the U.S. and Canada is an expensive and unresolved problem for the majority of steel companies. The Waelz process has been considered as the best process for treating EAF dust. A process model, combined thermodynamic modeling with heat transfer calculations, has been developed to simulate the chemical reactions, mass and heat transfer and heat balance in the kiln. The injection of air into the slag and the temperature profile along the kiln has been modeled. The effect of (CaO+MgO)/SiO2 on the solidus temperature of slag has been modeled also and discussed. Some optimizing results have been presented in this paper.

Jan 1, 2005

By Ivo André

Sorption of copper ions from aqueous solutions by dried biomass of the aquatic plant Potamogeton luscens was studied at laboratory scale. The aquatic plant was collected in water resources in Brazil, washed, dried at 60°C and ground in a bladed mixer. Sorption experiments were conducted in agitated flasks and in a packed bed column. Maximum copper removal was obtained between pH 5.0 and 6.6 when copper was present in the ionic form Cu'. Sorption followed the Langmuir isotherm with saturation attained at 35 mg/g. Free energy of sorption was found, to be of the order of -25 kJ/mol. Sorption kinetics data were better described by a second order reaction and rate constants were calculated in 0.030 1/(min.mg) for - 4.0 mm particles and 0.081 1/(min.mg) for - 0.59 mm particles. Removal of metal ions in a packed bed column showed that Potamogeton luscens biomass can be used in several sorption/dessorption cycles. After sorbent saturation, copper ions can be recovered from the loaded biomass by elution-with H2SO4, solution. Main mechanism responsible for heavy metal uptake was found to be ion exchange. Results are discussed in terms of the surface properties of the biomaterial, solution chemistry of copper ions and thermodynamics parameters.

Jan 1, 1995

02, NaCI03, H202, Na0CI and Ce+4 have been examined as oxidants in an alkaline carbonate system for uranium in in situ leaching. The South Texas and New Mexico ores contained up to 2.6 meqJg of reducing compounds which consume oxidants in the leading operation. Leaching rates did not increase linearly with the oxidation potential of the oxidants. A mild oxidant can be used to maximize uranium oxidation selectively and oxidant efficiency. 02 can oxidize most of the uranium mineral with an adequate rate and high oxidant efficiency.

Jan 1, 1990

By Chang Chia -Fu

The generic structure of our bimesogens is shown in and for a typical blue-phase mixture of the type we describe here. We use mixtures of the ratio 33.4% (n =2.6), 34.1% (n =6.57), 36.6% (n= 11.15) with of the high twisted power (HTP) agent BD H1381(available from Merck Chemicals and described in ref. We then studied the electric-field dependency of the selective reflection in BP I* at 20.7 °C by applying increasing and the decreasing pulsed alternating current (a.c.) electric fields (100 Hz).

Jan 1, 2006

By Rashmi Ramesh

Zinc oxide nanoparticles and nanostructures form an active area of research in the recent years. It can be doped to modify electronic, optical and other properties. Synthesis and characterization of zinc oxide is of extreme importance in order to understand the structure property relationship in this material which is now being considered of importance next to carbon nanotubes. Microstructure of zinc oxide nanomaterial is extremely sensitive to the preparation conditions. Nanocrystalline pure and Mn and Mg doped zinc oxide samples were prepared by wet-chemical method under different growth conditions. The samples were investigated for crystalline phase, microstructure, morphology and luminescence characteristics. The effect of Mn and Mg doping on the characteristics of ZnO have been discussed.

Jan 1, 2010

By Jae R. Lee

Keywords: Self-propagating high temperature synthesis, AlN, Powder synthesis The particle size and shape effects of starting raw powders on the synthesis of aluminum nitride by self-propagating high temperature technique under high nitrogen pressure were investigated with various AlN diluents and Al reactants. It was found that the structure of beds of the starting raw particles largely affected the pore channels for nitrogen gas infiltration as well as the passages for combustion propagation before and during the reaction, resulting in the morphology and purity changes of the synthesized products. The AlN product of purity over 98% with about 30 microns was obtained.

Jan 1, 2005

By Shirleny Fontes Santos

Muscovite mica crystals lower than 15 mm diameter are discarded as waste in the mining area of Borborema-Seridó (BRAZIL). The objective of this work was the ore dressing and purification of this waste to be used in the preparation of pearlescent pigment. Muscovite was dry ground using knife mills and an ultrasound treatment. It was possible to achieve 67% of mica with particle size lower than 100 µm. This product was used in the preparation of brilliant pigments based on muscovite flakes covered with rare earth oxides (CeO2, PrO2, Ce0,95Pr0,05O2). The pigments were characterized by X-ray diffraction, thermal analysis and scanning electronic microscopy. The color of the resulting pigments was analyzed using the CIELAB method and it showed the following colors: muscovite-CeO2 ? yellow, muscovite-PrO2? black and muscovite-Ce0,95Pr0,05O2 ? orange. Those results have shown that ?trash mica? is suitable for use in pigment preparation.

Jan 1, 2010