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By Victor Bredykhin

The report is devoted to the investigation and improvement of processes taking place at contact of large quantities of water insoluble liquid and particles of solid phase in a pulp. Theoretical analysis and simulation of acting conditions have allowed to determine that after attaching of oleophilic particles on the «water-reagent» separation surface the break of a formed complex is taking place according to the reagent volume and for oleophobic minerals along the «solid-reagent» separation surface. As a result particles are selectively treated if the magnitude of the reagent adhesion to the surface of solid phase in water is great. The results of dispersion are influenced significantly by availability of sharp edges on the surface of real particles. They keep tree phase perimeter of moistening. It is possible to fix reagent in the form of lens whose contact angle is significantly smaller in comparison to the thermodynamic angle. In adhesion dispersion the reduction of reagent volume, covering the equal area of particles surface is possible when the reagent is in a pulp in the form of thin films on the «water-gas» separation border. The process is tested in laboratory conditions as well as at pilot concentrating mills in flotation of sulfide ores, non-ferrous metals (copper-molybdenum ore), native sulfur and coal.

Jan 1, 2006

By Leonard J. Friedman

The contact process for the production of sulfuric acid has been used commercially since before the turn of the century (1880?s), and rapidly replaced the chamber process after the development of vanadium catalysts in the early 1900's (1910's - 1920's). Plant size has increased from a few tons per week to single train units in excess of 4,000 tons per day. Much of the history of the contact process is in the minds of the few remaining early process pioneers that started in the industry in the 1920's and 1930?s, and in sulfuric acid industry books published in 1921, 1925, 1936, and the last Deucker and West in 1959. Since those not familiar with history are doomed to repeat the failures and mistakes of the past, this paper includes a brief history of the contact process along with the history and development of equipment and materials in each equipment area of the process. The main focus of the paper is to present the development and analysis of equipment and materials in the contact section of the sulfuric acid plant - from the dry tower to stack.

Jan 1, 1999

By Hidekazu Nakagawa

We investigated the anodic dissolution behavior of titanium in TMHA-Tf2N molten salt, which has a wide electrochemical window of about 5 V, in order to develop an electrodeposition method for titanium. By etching a titanium electrode in HF?HNO3?H3PO4 solution, the titanium electrode became electrochemically active, and a redox reaction was observed at around -0.15 V vs. I-/I3- in (TMHA-Tf2N)?HTf2N solution. We identified the redox reaction consists of the reduction of the proton and the oxidation of hydrogen. The diffusion coefficient of the proton in TMHA-Tf2N was calculated to be 6.9 10-8 cm2 s-1 at 50 °C from the cathodic peak current in the cyclic voltammogram. Anodic decomposition of the molten salt was not observed up to 6.0 V vs. I-/I3- on titanium electrode, while it was observed at around 2.0 V vs. I-/I3- on platinum and glassy carbon electrodes. Cathodic decomposition of the molten salt was observed at around -3.0 V on the titanium electrode, as well as on the platinum and glassy carbon electrode.

Jan 1, 2006

By Vittorio Basilico, Marco Quattrone, Mario Bassan

"In Italian building market one of the reasons that often stop building contractors from not taking into consideration the possibility to recycle rubble from building is represented by the increase of costs for rubble separation. However the recycling of C&DW can also allow a decrease in disposal costs and a reduction in raw materials requirement.In this paper the results of a testing conducted on a case study through economic and technical analyses are presented.Results highlight that a wise management of demolition and disposal processes can generate a remarkable saving and that it is possible, on the other side, to achieve environmental benefits such as reduction of raw material consumption and dump life lengthening.IntroductionTwo major factors have been found to have considerably influenced the market of recycled aggregates in Europe and Italy: the EU and national regulations and environmental awareness. The market of recycled aggregate has grown in countries with limited natural resources.Waste disposal has also been one of the top EU political and environmental priorities. In the complex interaction between human activities and the environment, waste is proved to be one of the most environment-degrading products.In 1972 the European Commission introduced measures on waste reduction, reuse and recycling. In 2006, directive 2006/12/EC (European Commission) on waste was issued. It covers the scope of minimizing the waste, prevent hazardous waste, maximize reclamation, reuse, recycling and energy-recovery.No specific directive refers to management and recycling of construction and demolition wastes. However, in 1992 the European Commission listed debris among waste management priorities because of its growing amount.Only recently, effective environmental policies have been implemented in Italy, even though relevant environmental issues started rising as early as the beginning of the 1970s. In the 1980s the Government undertook the first significant measures to handle the waste management."

Jan 1, 2008

By Truan-Sheng Lui, Li-Hui Chen, Hao-Wen Hsueh, Fei-Yi Hung

"Since Ag wires have similar hardness and bonding properties to Au wires, they can be applied in some pads. In the present study, the annealing effect (at 225°C~275°C for 30min) on the tensile mechanical properties of silver wires with f=23µm was investigated. In addition, the micro-structural characteristics and the mechanical properties before and after an electric flame-off (EFO) process were also studied. Experimental results indicate that with annealing temperatures of more than 250°C, the silver wires possessed a fully annealed structure, the tensile strength and the hardness decreased, and the elongation was raised significantly. Under the thermal effect of EFO, the necks of the Ag balls underwent recrystallization and grain growth was induced, and the annealed Ag wires had a shorter zone of HAZ (220µm). The bonding strength and the neck-strength of the Ag wires were more than 7gf and possessed excellent bonding properties.IntroductionThermosonic ball bonding is one of the preferred processes for electronic packaging to connect a semiconductor chip and a lead frame by a thin metal wire. At present, gold wire and copper wire are the preferred interconnect materials to bond with the aluminum metallized wafer pads [1, 2]. Since gold is expensive and the reliability of copper is poorer [3], the study of silver wire has attracted a lot of attention already. In addition, the inherent properties of high ductility and low hardness of silver as well as its workability effectiveness compared to gold, have made it a preferred alternative .[4, 5]"

Jan 1, 2012

By Elsa Agante

Recycling of solid wastes, a common practice nowadays, requires the separation of the different materials in order to increase the products added value. The separation of one plastic from mixtures of different types of plastics is not easy due to their similar physical properties, but different techniques are available, from automatic sorting systems based on optical sensors to techniques adapted from mineral processing, namely gravity, froth flotation and electrostatic processes. In the last decade, many researchers have addressed the separation?s problem of different polymers, like Polyethylene Terephthalate (PET) and Polyvinyl Chloride (PVC), two polymers commonly used in packaging which have similar density. One proposed technique is the classical froth flotation performed in agitated cells. Froth flotation is a versatile and relatively cheap process widely used in mineral separation. It is based on the different behaviour of particles in the presence of an inter-phase air-water, which depends on the materials surfaces properties. Froth flotation can be affected by some variables such as impeller speed and air flow rate. Agitated cells, when used with low density materials, like plastics, can produce overstated turbulence that prevents the adhesion and collection of particles in the froths. In this case, separation is favoured by column flotation smoother hydrodynamics. This paper proposes the separation of PET from PVC by column flotation. The experimental work was carried out in a column of 9cm diameter and 1m high. The effects of some operating conditions, such as depressor and frother concentration, air flow rate and feed grain size on products grade and recovery were evaluated and the best flotation conditions for the separation of these plastics were established.

Jan 1, 2006

By F. Begazo

The most common approach to increase production in copper refineries is to increase current densities. However, if these increases are not well thought out beforehand and are not properly and effectively controlled, the end results could be reduced plant performance and a deterioration in cathode quality. Both of these factors result in lower efficiencies and increased costs. At the Ilo Refinery of Southern Peru Copper Corporation, a modernization and expansion program was implemented shortly after the Refinery was purchased from Minero Peru, in 1994. This program was intended to increase production from 195,200 mtpy of cathode to 227,000 mtpy over a 3-year period. Part of this production increase would come from increasing current density. During the period from 1994 to 1997, current density at the Ilo Refinery was increased from 218 A/m2 to 230 A/m2, while plant efficiencies were maintained at consistently high levels. The current efficiencies were maintained at >97.5% and time efficiencies were maintained at >98%. During 1998, additional increases in current density were implemented while the high plant performance was maintained at the same levels. By the end of 1998, the current density was 241 A/m2, while current efficiency and time efficiency of 98% were maintained. This paper describes the control processes used at the Ilo Refinery to maintain high plant performance levels while increasing the current density. Additionally, expected plant performances from extended test programs at current densities up to 280 A/m2, for future production increases, are reviewed and discussed.

Jan 1, 1999

By W. L. Cornell

Ore microscopy was used in support of both bench-and large-scale continuous beneficiation testing programs. Reflected light microscopy and Vickers hardness measurements were utilized to help identify problems relating to mineral identification, mineral association, mineral liberation, mineral distribution in product streams, and froth entrainment. Specimens studied were size fractions of concentrates and tailings resulting from Bureau of Mines research to recover a siegenite-enriched product by beneficiating chalcopyrite concentrates. Other specimens were size fractions of bulk sulfide concentrates recovered during the enhanced amine scavenging of final tailings by froth flotation. The findings from studies directly affected flowsheet development.

Jan 1, 1987

By Maria Margarida Lima, Maria Lucelinda Cunha, Dora Algarvio

"The main goal of the present work is the quality improvement of the recycled aggregates produced by a construction and demolition waste (C&DW) recycling facility located in Montemor-o-Novo, Portugal. The recycling process was developed on a pilot plant scale with 50 t/h of capacity. Process operations are the hammer mill comminution, magnetic separation and screening.In order to improve the knowledge on the C&DW, a characterization procedure was implemented by hand-sorting, magnetic and density separation on representative samples. On the other hand, to improve the quality of the produced aggregates, the bar screen size fractions were analysed, according to the Portuguese Standard (NP EN 933-1 2000).Wood was identified as the critical contaminant, representing 17% by weight of the total contaminants. Sieving results showed that about 97%, 76%, 56%, 98% and 57% were on the correct size range, which lower results are probably due to the type of screens and/or the material characteristics of the recycled aggregates.IntroductionThe construction and demolition waste problemConstruction and demolition waste (C&DW) is generated by the construction activity, resulting from both, buildings or other structures construction and old structures demolition. As a reference, it can be told that C&DW comprises about 40 to 50% of rubbish (concrete, asphalt, bricks, blocks and dirt), 20 to 30% of wood and related products and 20 to 30% of miscellaneous wastes [1]. In Portugal, C&DW is classified in the LER (Portuguese nick name for the European Waste List), Chapter 17, and includes a diversity of wastes, like concrete, bricks, ceramics, bricks, wood, glass, plaster, copper, zinc, lead, iron, steel, as well as insulation and roofing materials. C&DW stream has several characteristics which make it particularly difficult to deal with and are summarized in the following five items.(1) Lack of information on quantities generated: In Portugal, the C&DW sector has been neglected over the past years, which meant that there are not consistent information concerning the quantities and composition of these wastes yet. Several estimates, based in different assumptions, indicate different results, which may vary from 219 Mt to 10 931 Mt [2]."

Jan 1, 2008

By Joo Hyun Park

A history of the research regarding the spinel in the community of the stainless steels has simply been reviewed, followed by the recent studies for the formation mechanism of the spinel in the ferritic stainless steel melts equilibrated with the highly basic slags and the crystallization behavior of spinel phase in the calcium aluminosilicate melts containing MgO and CaF2 during slow cooling cycles. It has been proposed that the content of aluminum and calcium in the steel melts as well as the basicity and the content of MgO and Al2O3 in the slags are quite important factors affecting the spinel formation in view of the formation mechanism based on the reduction of MgO (or CaO) and Al2O3 in the slags by the aluminum and silicon added to deoxidize the molten steel. The use of magnesia refractory was also recommended. The formation mechanism of spinel from the MgO inclusions readily formed in the steel melts equilibrated with the highly basic slags has newly been proposed on the basis of the ionic exchange reactions at the inclusion/metal interface and the crystal chemistry of oxides. The crystallization behavior of the spinel phase in the calcium aluminosilicate melts was enhanced by the Al2O3 based on the ionic reaction of spinel formation in the oxide melts, while the size of the spinel crystals in the oxide melts decreased by addition of CaF2.

Jan 1, 2006

By K. V. Sreenivas Rao

Solidification experiments have been conducted to study the effect of interface heat flux and air gap formation on cooling rate of the casting during solidification of Al-4.5wt%Cu alloy. The thermal history of the casting and mold during solidification is recorded using thermocouples connected to computer interfaced data logger. The measured temperatures in the mold are used as input to the IHCP (inverse heat conduction problem) algorithm for simulating multiple heat flux components at the boundary. It is observed that the filling effects induce spatial variation in the thermal field in the mold and casting regions and greatly influence the cooling rate of the casting. The study demonstrates the use of IHCP and in-situ measured thermal profile in analyzing the cooling rate and microstructure.

Jan 1, 2008

By Takafumi Kondo, Satoshi Yamashita, Noboru Masuko

"Aqueous oxidation of phosphite ions to phosphate ions with dissolved oxygen was examined at 80° C and pH 4.5 mainly from the stichiometric point of view. Dissolved oxygen alone can not oxidize sodilim phosphite in aqueous solution, but when sulfur dioxide is coexistent, cooperative oxidation for both sulfite and phosphite can occur in aqueous solution. Sulfur dioxide itself is well known as a reducing agent, but it also reacts as an oxidation-promoting agent for other species under a certain condition. So sulfur dioxide is· a promising cheap reagent for waste phosphite processing.IntroductionIn a liquid-phase oxidation reaction using the dissolved oxygen gas, the eoexistence of a copper salt is required generally. Recently, it was reported that the oxidation reaction progressed by using mixed gas of sulfur dioxide and oxygen without the copper catalysis, and the attention has been collected1·3). The present authors also noticed the phenomenon since the early time and have been studying on the reaction mechanism of sulfur dioxide in liquid phase oxidation 4l. It was found that; by using the SO2-O2 mixed gas, the oxidation of phosphite ions to phosphate ions proceeded efficiently in sulfuric acid solutions. In the present report, the applicability of SO2-O2 mixed gas as a cheap oxidizing agent to the industrial processing of the waste solution of electroless nickel· plating is investigated. It is well known that the sulfur oxide dissolved in aqueous solution is oxidized ·by the oxygen in the air to sulfuric acid according to the following equation"

Jan 1, 2000

By Hans Hein

In its early stage of copper solvent extraction development, SX plants were designed in a series configuration and gradually the copper industry reduced staging and trains for keeping capital investments reasonably low. At a later date of its development, series parallel configuration was applied in some copper SX plants, particularly for increasing copper production at low copper tenor in pregnant leach solution. A gap between series and series parallel configuration had been observed for years. Conventional SX plants in series configuration frequently do not have the flexibility for maintaining designed or expected production level, whenever copper concentrations in pregnant leach solutions are getting low, whereas series parallel flow schemes almost require to double SX feed flows for achieving optimum results. A combined SX configuration breaks the gap and its application potentials are explained.

Jan 1, 2003

By A. W. Bryson, S. P. Fox, S. A. Godorr

"This work is an extension of a previous investigation on the development of surface roughness during electrodeposition of copper. A comprehensive model based on diffusion and migration in a force field together with surface diffusion and sticking probabilities is used to generate profiles which are compared to those produced experimentally. The roughness is characterized by using the technique of fractal geometry which is shown to describe both qualitatively and 9uantitatively the development of surface morphology during electrodeposition.The work is extended to the deposition of copper in the presence of various concentrations of thiourea. The development of roughness is observed experimentally on the edge of a thin copper disc mounted between two glass plates. This enables photographs to be taken at various stages during growth. The surface outline is digitized using an image analyzer which enables the fractal dimension to be determined as growth proceeds. As expected, the presence of thiourea at low concentrations produces a fractal dimension which is closer to unity (i.e. the surface becomes smoother).IntroductionThe development of surface morphology during electrodeposition has far-reaching implications for copper plating in the electrowinning and electrorefining processes. Short circuits as the cathode surface grows unevenly require operator intervention in a dangerous environment and imply processing delays, and the inclusion of electrolyte in small gaps in the plated cathode have implications in downstream processing of the cathode. Higher current densities are obviously desirable, as they result in greater production rates, but as shown by Ettel et. al.(l), Harvey et. al.(2), Cook (3), and Harvey et. al.(4), it is not possible to operate near the projected economically optimum conditions because the electrodeposition of copper from sulphate and acid solutions is a mass transfer controlled process. It has been shown (Ettel et. al.(l), Harvey et. al.(2)) that the closer a system operates to mass transfer limiting conditions, the poorer the resulting cathode quality. One solution is to use agitation techniques to increase the limiting current density. Another is to add surface active additives to the electrolyte which has been shown by Ettel et. al.(l), Harveyet. al.(2) and Afifi et. a1.(5) to allow higher rates of production without decreasing cathode quality. The second proposed solution is of interest in this work, since there is very little knowledge of the conditions under which these additives operate effectively, and little fundamental understanding of the mechanism by which they operate. The current work seeks to contribute to this field by correlating a simulation model with experimental results to describe the development of surface morphology in the electrodeposition process."

Jan 1, 1997

By A. Robles

The main goal of the present work is to propose a viable alternative for selective arsenic elimination from copper smelter flue dust without the need of a global leaching scheme for all the individual components of the flue dust. Using this alternative, the inherent copper recovery problems are avoided. Arsenic precipitation is also considered for regenerating the solution and completing the process cycle. The experimental results for arsenic extraction and precipitation are satisfactory. Concentration of NaOH used was relatively low. The main reason for succeeding in high arsenic extraction and low NaOH consumption is due to the previous water washing of the flue dust. Water washing dissolves much of the iron and copper that are present in certain percentage as sulphate.

Jan 1, 1999

By Alan DonaldsoN

Plasma Quench production of titanium is the thermal dissociation of titanium tetrachloride into gaseous titanium and chlorine followed by rapid quenching to prevent back reactions. Titanium tetrachloride dissociates into titanium and chlorine atoms at 5000 K. Expansion through a Delaval nozzle accelerates the gas to supersonic speed cooling it very rapidly. Cooling rates are as high as 7exp 1 0 Kelvins per second. Injected hydrogen reacts with condensed titanium particles to form titanium hydride and with the chlorine to form hydrogen chloride. We have produced titanium powder at 20 kglh in a continuous reactor. Costs are projected to be lower than the Kroll Process at large enough scale. Most of the cost reduction would result from elimination of magnesium as a reducing agent and much lower capital costs.

Jan 1, 2001

Korea has about 68 hundreds million tons of limestone's reserves. Still, high-Ca2+ limestone containing more than 52% calcium oxide makes up for about 12% only; hence the need for securing and effectively developing limestone. The best solution is to manufacture precipitated calcium carbonate (PCC). The synthesis of PCC using high-Ca2+ limestone has several advantages including the efficient development of resources and easing the import dependence on PCC. The first step is the selection of suitable limestone for the synthesis of PCC. In this study, formation age was decided as the primary key point, with its effect on calcination, hydration, and synthesis of aragonite investigated. Results showed that the yield of aragonite increased when newer limestone was used. On the other hand, neither the activity and bulk density of quicklime nor the particle size of aragonite was affected by the formation age, although special values were registered following each formation age. Moreover, the bulk density of quicklime and particle size of aragonite tended to increase with decreasing activity. This result is different from that of the other experiment. Therefore, a suitable method for measuring the activity of quicklime for use in the manufacture of PCC must be established.

Jan 1, 2006

By Mei Song, Qingyu Deng, Xuewei Lv, Lu Liu, Chenguang Bai, Meilong Hu

"The carbochlorination of several silica materials was carried out in the temperature range from 900 °C to 1200 °C. In this study, silica oxides and gaseous chlorine with carbon as reductant were used. The optimal carbon silica mole ratio in different temperature was calculated by Factsage software and the results showed that the optimal values are 1.2, 1.4, 1.6, 1.8 at 900 °C, 1000 °C, 1100 °C, 1200 °C, respectively. According to the experiments, the chlorination ratios of several silica materials were increased with temperature increasing. In the same temperature, the chlorination ratio of diatomite is the maximum and the chlorination ratio reaches 79%% when C/SiO2 reaches 3 at 1100 °C.1, IntroductionPolycrystalline silicon is the main material to manufacture the silicon polished section, solar battery[1] and high purity silicon wafers[2], also which is the most basic function material of semi-conductor industry, electronic information industry and solar photovoltaic battery industry[3]. The conventional manufacturing process of polycrystalline silicon would be divided into three parts: the improved Siemens method, which was introduced and became the main process to produce the polysilicon products in China. Silane method and fluidized bed method. Silicon tetrachloride and chlorosilans have been employed as by-products in several fields like electronic, telecounications and metallurgy[4-6]• At present, the main applications of silicon tetrachloride include production of trichlorosilane by catalytic hydrogenation, synthesis of fumed silica and ethyl orthosilicate, production of optical fiber grade silicon tetrachloride.The conventional routes for the silicon tetrachloride production have been reported, including the direct chlorination and the chlorination process of ferrosilicon, abandon catalyst and silica[7]."

Jan 1, 2013

By Mike Santaluce

Smelting furnace rebuild projects often require a significant capital expenditure and an extended smelter outage. Smelter operators are increasingly searching for methods and initiatives to shorten furnace rebuild schedules, maintain manageable cost levels, enhance furnace performance and achieve excellent safety results. This paper describes the ?MEPC? Model for furnace rebuilds; a project driven approach which Auburn has developed in response to the need for improving furnace rebuild project outcomes. The ?MEPC? (Management, Engineering, Procurement and Construction) approach better addresses the unique challenges presented by furnace rebuild projects when compared to the traditional EPCM (Engineering, Procurement, Construction Management) model widely in use for these projects today. One key feature of the MEPC model is that a dedicated project management team with representation from all of the major project stakeholder groups is put in place at the onset of the project. The project management team has ownership and accountability for meeting overall project goals over the entire lifecycle of the furnace rebuild project. A second key aspect of the model is emphasis on project management as a completely separate project function with its own specific skill sets, techniques, tools and best practices. These features of the MEPC model offer several advantages in terms of improved planning, coordination, communication and alignment with project goals which contribute to the overall success of furnace rebuild projects. Similar MEPC concepts have been used to deliver excellent project results in other industries and the MEPC approach has been successfully utilized on furnace rebuild projects.

Jan 1, 2006

By Gunther Klamp

Disposal of arsenic compounds from washing acid in metallurgical plants is becoming a severe problem when using lime neutralization. A further problem is the disposal of relatively large quantities of gypsum which is produced during this neutralization step and which Is also conta-minated with other toxic metal compounds. The Sachtleben-Lurgi process removes arsenic and other metals from washing acid in the form of insoluble sulphides. The purified acid contains less than 0.5 ppm of arsenic and can be used for standard sulphuric acid applications. The process Is demonstrated commercially at Sachtleben's acid plant since more than five years.

Jan 1, 1992