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By Duck Jae Lee, Kwan Ho Kim, Ji Whan Ahn

"In Korea, reutilization of constructions waste is gaining an increasing attention as generation of construction waste is projected to increase continuously. In current practices, the concrete waste is simply crushed and used as a low application such as paving, back filling, etc. In this study, a new process was developed comprising of heat pretreatment, autogenous milling, and density separation for complete reutilization of concrete waste. Firstly, the concrete waste was crushed using autogenous milling. The coarse size fractions from autogenous milling have a density of 2.5g/cm3 and a water absorption ration 3.0%, which meet the specification of the first class of KS F 2573. The fine size fractions were further separated using a hindered-settling column into two products 1) underflow, 2) overflow. The underflow sample was a high quality fine recycled aggregate which can be used for concrete making, and the overflow sample was an enriched cement material can be also used for CO2 sequestration by mineral carbonation. Introduction Kwan Ho Kim1, Ji Whan Ahn2, Duck Jae Lee1, Hee Chan Cho1 Recently, the importance of resource recycling is gaining a greater attention due to the increasing price of natural resource. Recycling is beneficial for not only the management of waste, but also the reducing of consumption of natural resources and huge energy consumption to treat of natural resource. The construction and demolition waste comprises the major industrial waste generated in Korea. It increased to 54 million tons in 2004, and is projected to increase to over 300 million tons in 2020, as many buildings reach the end of their 30 years life. Among total waste, the proportion of concrete waste was about 30% in Korea. Due to its large volume, recycling of concrete waste is the most important aspect of the waste management. In the current practices, the concrete waste is simply crushed and used as a recycled aggregate. The recycled aggregate has a low quality and most of them are down cycled for usage as paving material, back-filling material, concrete bricks, etc. It cannot be reused for replacement of natural aggregates because cement mortar is not separated perfectly from aggregates. These kinds of recycled aggregates tent to be weaker, more porous and have a higher value of water absorption. When these aggregates are used in concrete making, there are problems of higher total water demand, low compressive strength and durability [1-5]. And recycled fine aggregate is not almost recycled due to its low quality. In this study, a new processing circuit is developed to produce not only highquality recycled coarse aggregates but also fine aggregates and cement material from concrete waste."

Jan 1, 2008

By Luiz R. P. De Andrade Lima

This paper presents a mathematical model for the oxide copper ore heap leaching process. The data used in the model include physical-chemical, .geometrical and operational data, as: leachable metals ore contents, .flow rate and acid concentration, parameters of passivity, ore size distribution, the average residence time of the solution in the heap, height, irrigated area and weight of ore in the heap. In this model the heap is divided into horizontal and plane layers of constant area. The flow of the liquid in the heap is considered unidirectional and the solid-fluid reaction model is considered under diffusive control. The average residence time of the solution into the heap and the apparent effective diffusivity of the acid through the ore particles have .a significant influence on the rate of the copper extraction and its concentration in the pregnant solution; therefore these parameters are used in the model calibration. When this algorithm was applied to a laboratory test, the results showed that the model is adequate to predict the process performance.

Jan 1, 1999

By Nicholas S. Lynn

"A new process has been developed to bioleach refractory gold ores to expose the precious metal values using Thiobacillus ferrooxidans bacteria.The ore is hosted in a limestone rock with secondary replacement of carbonaceous and pyritic minerals. Crushing, stacking, bioleaching, rinsing and neutralization have been completed in a 45-day total time cycle. The use of sulfuric acid operation, and concentrated Thiobacillus ferrooxidans population allows the short bioleaching cycle.The ore is then processed using conventional Carbon-In-Leach Cyanide recovery techniques.ABSTRACT ONLY"

Jan 1, 1997

By Xie Gang

The leaching experiment used by bacteria on the low grade sulfide copper ore which is difficult to leach was carried out. Some leaching bacteria which have good physiological and leaching activity were isolated and domesticated, and were adapted to leaching ore. The effective domesticated method was put forward. Some technological parameters such as ore acidification, potential controlling, leaching method, ore granularity, leaching acidity, leaching liquid quantity and acid consumption were obtained by column experiment and leaching ore in situ under the ore well. The results show it could leach 30.62% of copper from the low-grade sulfide copper ore within 24 weeks by column leaching method, and the bioleaching rate of copper is 22.83% by leaching in situ under the ore well in 8 months.

Jan 1, 2006

By G. Cifuentes

When the applied current is interrupted in a copper electrowinning plant, and then is back in operation, the lead anodes tend to corrode. In order to decrease the corrosion, the damage protective ("back up") anodic currents are applied during the period of interruption. The current work aims to establish the effect of the concentrations of sulphuric acid, copper and cobalt on the anode corrosion, to quantify the effect of various anodic protection levels on the anode corrosion and to propose a method to select the appropriate protective current density value.

Jan 1, 1999

By Claire A. Chanenchuk

Catalytic Extraction Processing (CEP), a technology commercialized by Molten Metal Technology, Inc., a US.-based company, can convert industrial, household, and government wastes into commercial resources. CEP is an innovative elemental recycling technology that uses a molten metal bath to completely dissociate hazardous or toxic components of a feed and convert them to valuable products. The catalytic action of the molten metal bath converts the feed to its elemental constituents and the reducing atmosphere prevents the formation of any dangerous byproducts (NOx, SOx, dioxins, furans, etc.). Selective reactant addition allows engineering of valuable products from otherwise unexploited resources. Synthesis gas is generated from hydrocarbon feeds, ferro-alloys from metallic wastes, and ceramics from select inorganic species. Commercial-scale processing of multiple wastes and waste surrogates has been carried out at a destruction and removal efficiency exceeding 99.9999 wt.%, validating theoretical predictions. Unlike conventional hazardous waste treatment technologies, CEP offers resource recovery, minimal byproduct generation, and the potential for closed-loop recycling.

Jan 1, 1994

By David C. Lynch

The molecular form of trace elements in matte has been shown to depend on the chemical potential of sulfur and the propensity of the trace element to form a sulfide. Of the four trace elements (As, Sb, Bi and Pb) arsenic and lead behave nearly as opposites, with lead readily forming a sulfide while arsenic forms complexes with free copper and ion in the matte. Antimony and bismuth both display the dissolution characteristics as As and Pb, suggesting that these elements dissolve in matte in multiple forms of significant concentration. While in the present investigation the dissolution characteristics of all four trace elements are examined, the primary focus is on the multiple dissolution behavior of Sb and Bi.

Jan 1, 1995

By Ray Y. Lin

This study explores the formation of sodium pyrosulfate in molten sodium sulfate resulting from dissolution of SO3 at temperatures between 1160 and 1250 K. Solubility of SO3 in Na2SO4 melts at temperatures between 1160 and 1250 K under gas mixtures of SO2, O2 and argon was investigated applying a thermogravemetric analysis (TGA) technique. The activity of Na2O in the melt was determined with a high temperature electrochemical cell (ECC). Results showed that the SO3 solubility in molten Na2SO4 increases with decreasing temperatures and increasing SO3 partial pressures. Enthalpy of SO3 dissolution in molten Na2SO4 was calculated to be -119 kJ/mol for infinite dilute solutions. Thermochemistry of Na2SO4-Na2S2O7 melts was analyzed based on information obtained from both TGA and ECC techniques. Detailed examinations of the earlier low temperature measurements in the Na2SO4-Na2S2O7 system along with data from this study reveal that the solution behavior between Na2SO4 and Na2S2O7 can be satisfactorily treated as regular with the interaction parameter, , being 2.7 kJ/mol. The phase diagram and the field of SO3 partial pressure has been generated with the thermodynamic calculation using a regular solution approach.

Jan 1, 2006

By Xu Zhong

The theoretical limit to smelting rate and possibly the size of a smelter is dependent on the rate of heat transfer, and the chemical kinetics of both sulfur removal and minor element volatilization. The fundamental kinetics of volatilization of minor elements such as As, Sb, Bi, and Pb from matte and white metal is being investigated. It has been shown that the molecular form of trace elements in matte depends on the chemical potential of sulfur and the propensity for the minor element to form a sulfide. The impact of the variable molecular form of the minor elements on the volatilization kinetics is unknown and is under investigation in this study. The experimental technique is reviewed and preliminary results are reported in this manuscript.

Jan 1, 1995

By Milan Lj. Stamatovic

The hydrometallurgical recovery of zinc from recycled blast furnace dust from a steel plant (Smederevo Metallurgical Company - Yugoslavia) was investigated. The dust contained 22% Fe, 17% Zn and 0.2% Pb. X-ray diffractometry showed that the main components were hematite and magnetite, in combination with zinc oxide and a very low content of lead oxide. Individual particles were generally spherical and ranged in size from 10 to 150 microns; 63% were less than 33 microns in diameter. An effective hydrometallurgical approach proved to be by caustic leaching followed by electrowinning. Recovery of zinc in the form of zinc powder was over 90%. This powder can be used for the cementation of impurities in the conventional hydrometallurgical process for zinc production.

Jan 1, 1993

By Chen Yongming

In order to eliminate the serious environmental pollution caused by low concentration of sulfur dioxide smoke in antimony smelters, a new smelting process, named as reducing-matting smelting, is proposed in this paper. The effects of technical conditions such as smelting temperature, smelting time, Pyrite cinder addition and the amount of additive on the smelting of stibnite concentrate have been investigated by the method of single-factor experiment. The results show that the optimum conditions are as follow: The amount of pyrite cinder is 1.2 times of its theoretical amount. The addition of soda and sodium sulfate is 15% and 72.6%, respectively, to the amount of stibnite concentrate when the total amount of sodium is 30%. The reducing-matting smelting is conducted at 1100°C for 2h then the smelting temperature is raised to 1200°C for 50min. Under the optimum conditions, the direct and total recovery ratio of antimony can gain 90.99% and 98.87%, respectively, and the fixed ratio of sulfur is higher than 99%.

Jan 1, 2006

By Jimsher Aneli

The investigation of some peculiarities of conductivity dependence on filler type and amount in the polymer composites has been conducted. It is established, that conductivity of composites based on phenolformaldehide resin essentially depends on proportion of double fillers: graphite + carbon black, graphite+ andesite, contained in composites. It was shown, that these composites characterized by synergetic effect ? non additive influence of fillers concentration on the conductivity of composites. Some other properties of composites contained binary fillers (effect of temperature and pressure on the conductivity) have been investigated.

Jan 1, 2006

By Luis G. S. Sobral, Gabrielle N. Bard

Copper sulphides Concentrates, from the flotation process of copper primary ore; contain, commonly, small amounts of precious metals, such as gold and silver. During the smelting process of those concentrate all gold and silver are practically in the blister copper, which is cast into anodes. Those copper anodes are electrorefined in an electrolytic system, where the electrolyte is an acid copper sulphate solution, where a high purity electrolytic copper is produced (>999,9/1000). The slime when submitted to an oxidative leaching process, using sodium hypochlorite and hydrogen peroxide as oxidizing agents, turn those metals into solution. This research practical work, apart from concentrating effort on the digestion of the anode slime, aims at evaluating the efficiency of the cementation process of the metals of interest for the separation of them to take place. 141

Jan 1, 2008

By Shadia J. Ikhmayies

"Nanocrystalline CdS thin films were prepared by vacuum evaporation on glass substrates at ambient temperature. The films were characterized by recording and analyzing their transmittance, X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) images and Energy dispersive X-ray (EDAX) spectra. X-ray diffractograms revealed that the material is nanocrystalline with predominant cubic crystal structure and preferential orientation along (1 1 1) plane. SEM micrographs confirmed the nanostructure of the material and showed uniform and well covered surfaces. EDAX reports revealed that the films are cadmium rich and contain oxygen. The first derivative of the absorbance was used to estimate the effective bandgap energies of the nanocrystallites and the hyperbolic band model was used to estimate their radii. The results were compared with those obtained by XRD and SEM measurements.IntroductionCdS thin films are of considerable interest as they can be used in fabrication of solar cells and other opto-electronic devices. In particular, heterojunction solar cells with a narrow band gap base and wide band gap window have been investigated in an attempt to develop efficient, stable and low-cost solar cells [1]. The CdS quantum dot embedded in a glass matrix is one of the well-known quantum dot systems and its electronic and luminescent properties have been studied extensively [2].Three-dimensional confinement of carriers within the quantum dots leads to the blue shift of the optical band-gap and to modification of many properties of semiconductor material [3]. It has been argued that in these semiconductor nanoparticles the hyperbolic band model gives a better fit to the observed quantum size effect as compared to the effective mass approximation [4]."

Jan 1, 2012

By Sergio Demetrio

Over a period of nearly a hundred years throughout this century, the company direction and management of copper smelters in Chile has evolved from one characteristised by a paternalistic, autocratic style to one which empowers the local management team and people for running the smelter as a successful business. This paper discusses the evolution of the present style of management amidst changes in the Chilean Government, the mining industry and society since the beginning of this century.

Jan 1, 1999

By Antonio de Ita, Isaias Hilerio, Miguel Barron

"The influence of an unconventional lance with a central nozzle on the multiphase fluid flow in a steelmaking converter is studied in this work by means of computer simulations. The lance has four peripheral supersonic nozzles and a vertical central nozzle. Besides, the oxygen flow in the central nozzle is considered independent from the main oxygen supply. Transient two-dimensional numerical simulations were carried out considering just molten steel and gaseous oxygen as the existing phases. Numerical results show that bath agitation and droplet generation are enhanced as a result of the central nozzle. However, the performance of this lance strongly depends on the distance of the lance tip to the molten steel surface and the velocity of the oxygen jet.IntroductionCurrently, two thirds of the world crude steel is produced through the steelmaking oxygen converter [1]. Given the unquestionable economic importance of this technology, any improvement or optimization proposal is welcome. In the majority of current oxygen converters a top oxygen supersonic jet is blown onto the molten steel through a water-cooled lance to eliminate by oxidation some impurities such as carbon and phosphorus. Conventional lances have inclined peripheral nozzles whose number depends on the converter capacity. During the process, a large amount of gases evolves, forming metal droplets and a metal-slag-gas emulsion [2]. The droplets and the resultant emulsion increase the reaction interfacial area, promoting in this way carbon removal and dephosphorization of the molten steel bath [3]. However, during the blowing stage, the emulsion rises towards the lance and converter mouth and frequently forms layers which accumulate in the lance, reducing the life of the lance tip [4, 5]. It is possible that some freezing of the molten metal occurs due to the low oxygen injection temperature, however there are no reports on this. Besides, frequently undesirable operating phenomena such as spitting and slopping may arise as a result of inappropriate blowing practices or bad lance design. In the oxygen steelmaking industry, novel lances design are needed in order to enhance the decaburization rate and the slag formation and, at the same time, preventing operating practices that decrease productivity and move away the shop from safety standards."

Jan 1, 2012

By K. Watling

Vibrational spectra of surface and solution compounds formed during cyclic voltammetry of a gold electrode in a deoxygenated 0.01 mol dm-3 NaCN solution have been examined using surface-enhanced Raman scattering (SERS) spectroscopy. The presence of cyanide at the electrode surface was indicated by Raman bands characteristic of the carbon-nitrogen stretch, CN.. Chemisorption of cyanide on the gold surface was evidenced by the presence of vibrational modes due to gold-carbon stretching, AuC, and gold-carbon-nitrogen bending, AuCN. Prior to the disappearance of the surface cyanide stretch band, a limiting value of the CN was obtained, the same as the value reported for adsorbed cyanide. Effects upon the voltammetry and vibrational modes of surface species due to additions of silver and lead to the gold-cyanide system have been observed.

Jan 1, 2003

By T. A. Edison

A distinct hydrocarbon maturation anomaly coincides with the Gold Acres open pit, Nevada (Figure 1). Both atomic hydrogen to carbon (H-C) ratios and reflectance measurements of contained organic matter indicate significantly higher maturity in samples collected within the confines of the open pit than in samples from the surrounding region (not shown in Figure 1).

Jan 1, 1987

By Jean-François Domgin

This paper aims at presenting numerical results showing the impact of different parameters on the limitation of entrained slag from ladle to tundish during the ladle drainage. These parameters are process parameters, slag properties or external actuator acting directly on ladle slag behaviour. Numerical simulations based on the use of the CFD Fluent software illustrate the vortexing and non-vortexing phenomena appearing during the ladle drainage. This numerical tool validated by experimental data acquired on water model has been applied to industrial configurations. It shows that the slag properties (viscosity, surface tension?) or some modifications of parameters (slide gate opening, geometry of the ladle bottom?) have a positive effect on the slag entrainment and also on the decrease of the ladle heel. Finally, the modelling of the behaviour of an external actuator injecting some gas in the region of the nozzle reveals interesting possibility for reducing slag entrainment from ladle to tundish during the final steps of the drainage.

Jan 1, 2006

By Takeshi Yoshikawa

For the sake of effective control of titanium-compound inclusions in the steel-making processes, especially for stainless steel production, the influences of alloying elements of chromium, nickel, manganese, molybdenum, copper and oxygen on the thermodynamic property of titanium in molten iron were investigated at 1873K. At a certain titanium potential controlled by the coexistence of Ti3O5 and Ti2O3 doubly saturation of steels, the interaction parameters between alloying elements and titanium in molten iron were determined as follows. [ ] From the investigations on the equilibrium of titanium deoxidation in molten iron, the activity coefficient of titanium and the first order interaction parameter between oxygen and titanium were determined as follows. [ ] Also, deoxidation equilibrium for titanium in molten 304 stainless steel was measured and compared with the calculated results using the determined interaction parameters.

Jan 1, 2006