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By Tam Tran

Most new gold mines in Australia are required to treat tailings to reduce cyanide levels before they are discharged to storage ponds to meet the stringent environmental management guidelines set by government statutory authorities. In New South Wales, the average level of weak acid dissociable cyanide allowed in open tailings dams is now limited to 20 ppm, As stringent environmental guidelines continue to be enforced in Australia as well as in other parts of the world, the management of cyanide wastes has emerged as a key issue for the gold mining industry. This paper provides a critical evaluation on technical aspects related to the use of ion exchange resins and affiliated processes in cyanide management and tailing treatment. Particular attention is given to the use of ion exchange resin technologies in the processing of mixed gold-copper ores, where cyanide usage is the highest. Information presented in this paper is heavily drawn from the experience on the application of ion exchange resin processes at May Day mine, in New South Wales, Australia and associated pilot plant test programs. Issues related to the management of thiocyanate, especially with respect to the recovery of cyanide from thiocyanate are also discussed.

Jan 1, 1998

By Ajit Kumar Jaiswal

"Electric Arc Furnace (EAF) being a power-intensive equipment, EAF based industries are highly dependent on scarce electric energy. This is the reason Government of India is highly concerned about this and laid emphasis on the conservation of electric energy.This paper highlights factors contributing to reduction in specific electric energy consumption in EAF and suggests measures not only for power saving, but also for productivity improvement. To name a few, these are proper sealing of furnace, introduction of oxy-fuel burners, foamy slag practice, increased usage of hot metal/DRI, post-combustion of CO gas for preheating of scrap, improved selection & design criteria of electrics, power demand management, and process automation. Few cases also have been cited, where the above measures have helped in reaping significant benefits.IntroductionFor a long time, Government of India had focused on increase in energy supply, in particular, through electricity generation. Now the emphasis of Government of India has shifted from electricity generation to its conservation for following two reasons:??Power plants have become very cost-intensive??By saving energy, more of it can be delivered at lower cost to the consumersPower generating units, transmission & distribution agencies as well as consumers all have roles to play in the area of energy conservation. By energy conservation, we mean curtailing energy requirement by reducing energy wastages and taking up measures to improve energy efficiency of electric equipment/appliances. In almost all cases, this would be economically beneficial.India’s cost-effective energy conservation potential has been estimated by the Planning Commission at 23 per cent of total commercial energy generated ?1?. A national movement for energy conservation can significantly reduce the need for fresh investment in energy supply systems in coming years. It is imperative that we make all-out effort to realize this potential. Whether a household or a factory, a small shop or a large commercial building, a farmer or an office worker, every user can and must make this effort for his own benefit and for the nation’s benefit as well."

Jan 1, 2009

By Y. H. Liu

Several foaming aluminum samples of different density were prepared in a semi?industrial scale experimental system, Their properties such as the energy absorption characteristics, mechanical properties, heat conductivity and acoustical properties were measured. The results showed that the foaming aluminum with a density of 0.5 to 0.6 g/em3J has the best energy absorption and this makes it suitable as the ensuring bar of the automobiles and also as a cushion material for the engine. The foaming aluminum with a density of 0.25 to 0.4 g/em3 has the best acoustical properties and heat conductivity resistance, which is suitable for the door filling material, the ceiling and the partition or the car engine.

Jan 1, 2003

By In-Hyeok Choi

Currently, spent V2O5–WO3/TiO2 catalysts contribute significant amounts of solid waste following increasing levels of global demand. V2O5–WO3/ TiO2 catalysts usually consist of TiO2 anatase as a supporting oxide, vanadium as a catalytic agent, and other promoters such as tungsten, silicon, and calcium. Although vanadium is the main catalytic agent, a relatively high content of tungsten (WO3, 7–10 wt%) typically exists compared to vanadium (0.5–1.5 wt%). Considering the irreplaceable properties and industrial importance of tungsten, a feasible method for the recycling of spent V2O5–WO3/TiO2 catalyst should be established to utilize it as a secondary source. This paper presents a process to recover tungsten from spent V2O5–WO3/TiO2 catalyst. The processes proposed here involving roasting, decomposition using HCl, ammonia leaching, and crystallization. Within the process, ammonium paratungstate (71 wt% as WO3) is obtained as a final product. The total yield rate of tungsten from feedstock was found to be 96.3%.

By Ying-Chu Hoh

The extraction of cerium(IV) by valence change with two-phase electrolysis was studied experimentally. The results show that the electro-oxidation extraction depends mainly on the distribution of the solute between the two phases, the reaction on the electrode surface and the diffusion of the reactant and product between the electrode and aqueous interphases. The effects of various parameters on cerium extraction were also studied. The selected parameters were background current, catholyte acidity, agitation speed, operation current and voltage and surfactant addition. The electro-oxidation extraction mechanism can be divided into eight steps. In addition, Wee the rate of extraction is quite fast, the percentage extraction Ce+4 can be taken as an index to show the conversion rate of Ce+3 J to Ce+4.

Jan 1, 1989

By Ma Ying

The continuous directional solidification technique of five kinds of special ZA alloys with eutectic, peritectic and eutectoid transformation 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 Maria G. Alves, Alexandre M. Stumbo, Francisca M. A. Pinheiro, Jonas Alexandre, Sergio N. Monteiro, Valdo da S. Marques, Paulo R. N. da Silva

"Brazil is among the few countries with potential for developing all sources of renewable forms of energy. In particular, the country is leading the world efforts of substituting petroleum based fuels for biofuels, such as ethanol and biodiesel. Most of the Brazilian petroleum, which has now achieved self sufficiency, is extracted from offshore wells located at the north region of the state of Rio de Janeiro. In view of the future depletion of petroleum, the State University of the Northern Rio de Janeiro (UENF) has created a Center for Alternative Energies (NEAL) to carry out R&D programs on renewable forms of energy. Today, the main project of the NEAL/UENF is a model park for generation of renewable forms of energy. The objective of this work is to present the structural concept of the park and discuss its contribution in terms of scientific, technological, economical and environmental benefitsIntroductionEnergy is presently a key issue in the world agenda for sustained development and environmental protection. It is of common agreement that the existing status of increasing use of fossil fuels, mainly petroleum, natural gas and coal will not only cause depletion of these resources with a consequent elevation in price but also climate changes, especially global warming. In fact, the humankind may be already facing an irreversible situation of climate alterations as well as reduction of conventional sources of energy. The worse predictions foreseen by specialists, still for this coming century, are dramatic disasters due to catastrophic weather in association with a profound energetic crisis. This scenario may, however, be avoided by actions that could effectively tackle the core of the problem. These actions have been suggested and discussed by scientists and leading authorities, especially in international symposia [1-3]. In particular, the Kyoto Protocol proposed goals for reduction of greenhouse gas emissions as well as a mechanism of carbon credits to allow for decreasing CO2 content in the atmosphere without affecting industrial production [3]."

Jan 1, 2008

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 Robert M. Leary

The Kennecott Utah Copper smelter operates two Outokumpu flash furnaces: a smelting furnace for production of high-grade matte and a converting furnace for production of blister copper. Flash furnaces typically possess several characteristic features that must be considered in process control development such as long lag times associated with settler volume, non-linear input and output responses, large process gains, and unmeasured disturbances. Additionally, the Kennecott smelter possesses certain unique characteristics which must be considered such as single mine concentrate source, limited concentrate blending capacity, and feed preparation facilities that inevitably cause significant lags between furnace control parameters and manipulated set points. In order to improve furnace control and on-line time, a process control system was developed to address these issues. The feed forward control module provides predictive control and operates in response to furnace feed input changes. The feed back control module provides responsive control and is based on furnace output deviations. To provide regular feed back information to the control room supervisors, new sampling methods were developed which provide the operators with molten metal and bulk material samples at regular intervals to provide information for control. The control system was implemented on the Flash Converting Furnace in May 1999 and on the Flash Smelting Furnace in August 1999.

Jan 1, 2000

By Takashi Araki

In this work, we have elucidated the two-step oxidative reaction mechanism of 2,4,5-trichlorophenol by adsorbing oxygen atom for oxidative decomposition reaction of 2,4,5-trichlorophenol on oxide catalyst surface using ab initio molecular orbital calculation. In the first oxidation, total energies of reaction products have been shown extremely stabilized at all oxidation positions. This reaction occurs due to charge transfer from benzene ring to adsorbing oxygen atom. As a result, 1£ bonding of benzene ring are weakened. However, the benzene ring of 2,4,5-trichlorophenol does not perform cleavage reaction. In the second oxidation, the benzene ring of2,4,5-trichlorophenol can perform cleavage reaction, since the second oxidation obtains larger stabilized energies than the first oxidation.

Jan 1, 2003

By D. S. Barr

Mineralogical, lithological, and metallurgical studies were conducted on various gold ore deposits currently controlled by Freeport-McMoRan Gold Company. Ore samples were first lithologically and mineralogically categorized, then subjected to chlorination, roasting, and autoclaving pretreatments to determine their effects on gold recovery in a subsequent alkaline cyanide carbon-in-leach extraction. The studies indicate that, while organic carbon and sulfide sulfur are the primary refractory components, their effect on process response must be interpreted with respect to the deposit's geology and mineralogy. This approach has proven to be an effective method for evaluating metallurgical alternatives and fore-casting future mill performance.

Jan 1, 1987

By Valeriano Antonio Corbellini, Marilda Macagnan, Rosana de Cassia de Souza Schneider, Tiago Bjerk, Mariela de Souza Vieira

The great potential of Brazil for the agricultural production makes our country a generator of agro industrial residues. In this context, the solid-state fermentation appears as a technology that shows alternative ways for those residues, adding values to these raw materials, through the production of substances of industrial interest, besides reducing the possible environmental problems. The main objective of this study was to apply the bovine fat residue associated to the garden grass for the fungal lipase production. Initially, 75 microbial cultures were isolated from garden grass samples after incubation of the mixture with bovine fat. From these cultures were selected the filamentous fungi, whose lipase production abilities were evaluated. The isolation and the selection were accomplished by using a differential culture medium containing Tween 80 as inducer substrate of lipase production. The colonies with lipolytic potential were detected by the presence of white precipitation haloes on the agar. With agro industrial residues the best lipase producer fungus was identified as Penicillium sp in 6 days of solid state fermentation. The crude enzyme obtained was tested in transesterification process for the biodiesel production.

Jan 1, 2008

By Leonardo Mota, Lucas L. da Costa, Milton B. Filho, Sergio N. Monteiro, Helion Vargas, Tammy G. R. Portela da Silva

"A natural biofoam extracted from the buriti palm tree has shown characteristics for potential substitution of synthetic foams. In the present work, a photoacoustic thermal characterization was performed on buriti biofoam samples. An open photoacoustic cell technique and a photothermal rise method performed under continuous laser illumination were employed in order to determine the thermal diffusivity and the specific heat capacity of such material. In addition to their intrinsic values (finger print), these physical parameters represent the light-into-heat conversion efficiency and the amount of heat stored per unit volume, respectively. The results showed that the buriti biofoam presents thermal properties that permit its use as an effective insulation material.IntroductionSolid foams are very light materials with increasing engineering applications [1]. A natural biofoam obtained from the petiole of the buriti palm tree (Mauritia flexuosa) has been recently investigated [2-4]. The evaluation of the buriti biofoam properties and the characterization of its microstructural aspects have shown that this biofoam has a potential as a new engineering material with very low density. Additionally, its reduced open porosity and low absorbed humidity revealed a promising material for packing and floating applications. In fact, this buriti biofoam, extracted from the palm tree natural of the north region of Brazil, is being used by the low income population as a modest substitute for Styrofoam® [1].As a potential insulating material, the buriti foam needs to be characterized in terms of its thermal and acoustic properties. A preliminary investigation [3] on the thermal behavior of this natural biofoam by thermogravimetric analysis, TGA, and its derivative, DTG, as well as differential scanning calorimetry, DSC, revealed parametric conditions associated with water loss and structural decomposition. Both the surface humidity and the release of hydration water were determined. Different decomposition events were attributed to both, more rigid as well as to more flexible molecular segments. Table 1 depicts technical data obtained so far for the buriti biofoam. These data are compared to those corresponding to Styrofoam®."

Jan 1, 2011

By F. Kassabji

This publication presents the main experimental and theoretical results on the recovery of aluminum scrap (dross and Used Beverage Can) without use of any addition of fluxing salts. Dross and UBC's processing experiments have been conducted in a rotary plasma furnace operating in the transferred and non-transferred mode, using different plasma gases. The investigation involved the treatment of more than 100 kg of dross and other aluminum residues using plasma torches with less than 100 kW power. The experimental work showed that this process is .far more economical and kind to the environment than the conventional route using a salt flux. An equilibrium thermodynamic calculation at elevated temperature makes possible the prediction of by-products at various temperatures for different plasma gases.

Jan 1, 1994

By Beate Ina Jenssen

Ferric iron removal from the nickel electrolyte at Glencore Nikkelverk AS in Kristiansand, Norway, is achieved by precipitation of iron hydroxide followed by filtration, and it is desirable to improve filtration properties of the precipitated iron hydroxide in order to decrease the filtration time. The effect of increasing the residence time from the current 45 min to 75 min and temperature from 65 °C to 90 °C on the filtration properties of the precipitated iron hydroxide (akaganéite) was studied by simulating the industrial process conditions in a continuous reactor setup operating at steady state, using ferrous-containing process solution as feed material. It was possible to decrease the filter cake resistance by both increasing residence time and temperature, but temperature gave the most pronounced effect and reduced the filter cake resistance by one order of magnitude.

By Pandey H. D.

The paper describes a fluidised bed ion exchange method for simultaneous removal of phenols and cyanide from the effluent. Use of an eluant enables regeneration of the resin in the continuous operation mode. The breakthrough experiments conducted both on the laboratory scale and on a pilot plant scale have shown that while the level of phenol can be brought down from 462 ppm to about 6 ppm, the free cyanide is almost totally removed. An examination of data indicates that the method can serve the twin objectives of pollution control and phenolic compounds recovery.

Jan 1, 1992

By Pengkai Wang, Huimin Lu, Xiaoxiang Zhang

"In this paper, it was studied an electrochemical reduction process of carbon dioxide in ionic liquids such as 1-n-butyl-3-methylimidazolium hexafluorophosphate ([Bmim] PF6) as the electrolyte. The electrolysis experiments were carried out under current and potential controls. The cathode products contained carbon nanotubes, carbon nanofibers, nanographites, and amorphous carbon. To establish the actual current and potential ranges, the electroreduction of carbon dioxide dissolved in the ionic liquid was studied by cyclic voltammetry on glass-carbon (GC) electrode at room temperature. The electrochemical mechanism of carbon dioxide electroreduction was studied for explanation of all obtained results. Carbon dioxide in ionic liquids was electroreduced, similar to metals oxides being electroreduced in molten salts.IntroductionGlobal warming caused by the increase of carbon dioxide in the atmosphere has become one of the most concerning environment problems, so the solution to this greenhouse effect is very urgent. However, the carbon dioxide is also a cheap and abundant raw material that represents a potential source for the production of chemicals and fuels. Therefore, the development of the technologies that achieve simultaneous reduction and conversion of carbon dioxide to fuels is important. The electrochemical reduction of carbon dioxide is one of the effective approaches to transform CO2. Many investigations have been carried out on the electrochemical reduction of CO2 in both aqueous [1] and non-aqueous [2] electrolyte solutions with different electrodes. The solubility of CO2 in water is very low even under high pressure of CO2, and some investigators have brought focus into the electrochemical reduction of carbon dioxide in organic solvents, because they dissolved much more CO2 than water did. However, the hazardous or toxic properties of organic solvents hinder their use."

Jan 1, 2009

By Deventer Johanna van

Ore bodies around the world are declining in grade, whilst increasing in complexity. The level of impurities relative to the valuable metal is steadily increasing, posing new challenges to existing operations. Ion exchange is widely used in the hydrometallurgical industry for both primary recovery of metals and the removal of impurities. The superior selectivity of ion exchange resins makes them exceptionally suitable for the removal of target impurities to very low levels, thereby saving operating costs, increasing the value of the final product and significantly improving revenue. The ion exchange process in these applications is very simple, using standard ion exchange equipment and acid regeneration. The process can be fully automated, requiring minimal operator interference and supervision Examples of impurities that are successfully removed via ion exchange include iron, antimony and bismuth from copper electrolyte. In the copper electrolysis process, antimony, bismuth and arsenic tend to form slimes which are dispersed in the electrolyte. These slimes contaminate the cathode and/or decrease the quality of the copper deposition. A special chelating resin was developed to remove antimony and bismuth, while at the same time ensuring minimal chloride leakage to the sulphate matrix. The work is described in more detail in this paper. Ion exchange is also used to remove copper, zinc and nickel from cobalt electrolyte. This paper addresses a few of these examples in more detail.

By S. Abe

Various copper anodes to be electrorefined were subjected to a heat treatment comprising annealing at a temperature in the range of 700 °c to 1,000 °c followed by a slow cooling preferably on the order of about 150 °c, and using these heat treated anodes , a series of dissolution experiments were conducted under conventional electrorefining conditions. The results obtained have indicated that the above annealing/slow cooling process dramatically improves the dissolution activity regardless of the type of anodes. As an example, passivation times of l to 3 minutes in a standard test have been increased to more than 80 minutes by this innovated heat treatment. Other advantages sterning from the improved anodic activity include reduced electrical short circuiting which results in substantial labor effort in the tankhouse, reduced energy requirement, and reduced cost of processing anode slimes because the amount of anode slimes is reduced. In addition, this process gives rise to a dramatic change in the nature of anode slime layer formed in such a way that a comparable final cathode copper product can be achieved even from high-impurity copper starting material.

Jan 1, 1987

By I. G. L. Sinclair

The Selbaie deposit is located in northern Quebec. It is comprised of three distinct, but genetically related, Cu-Zn-Ag ore bodies which also contain economically significant amounts of Au. The deposits are Archean in age and volcanogenic in origin. At Selbaie, ore microscopy has been employed to aid in planning of ore beneficiation methods and to monitor the ongoing performance of the concentrator. Examples of both types of study are described. Early in the life of the mine, excessive amounts of Zn appearing were found to be appearing in the Cu concentrate. Microscopic examination of concentrates showed that this was being caused by the presence of coatings of supergene chalcocite on sphalerite grains. Fine coatings of supergene galena and chalcopyrite were also observed on some sphalerite grains. The presence of Ag and Au in the ores makes an important contribution to the revenue of the mine. The various modes of occurrence and mineralogical relationship of these two metals are described and discussed. Monitoring of the ongoing concentrating process at selbaie is done by qua-litative and quantitative examination of products collected at various points along the circuit. Causes of such problems as excessive loss of metals to the tailings or inefficient recovery of individual metals, can often be identified and possible solutions proposed.

Jan 1, 1989