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By Ma Ying

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

Jan 1, 2003

By Zhuo Sheng

We have designed a high-temperature Raman micro-furnace and cell that is suited for the electrochemical process study of the NO3 − in molten NaNO3– KNO3 (fraction of NaNO3 50 wt%) salt. During the cycle voltammetry and constant potential electrolysis process, the Raman laser beam was focused near the electrode; subsequently, the Raman spectra are obtained and the reduction process of NO3 − is analyzed. In the CV cathodic scan process, the new peak attributed to the ν1 mode of NO2 − emerges, and the peaks assigned to superoxide ions (O2 −) and peroxide ions (O2 2−) are not found. In the constant electrolysis process, the peaks at 1130 and 800 cm−1 appear when the potentials are between −2.0 V and −3.2 V (vs. Pt). The results show that when the NO3 − is reduced in molten the NaNO3–KNO3 mixtures, the reduction product O2− cannot stably exist, and O2− will react with NO3 − to form of superoxide ions (O2 −) and peroxide ions (O2 2−).

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 Christiana Mystrioti

Greece is the only EU country with extensive nickel laterite deposits. Since the 1960s, the Greek laterites are treated for ferronickel production via a pyrometallurgical route, which involves pre-reduction of the ore in rotary kilns and reduction smelting in electric arc furnaces. Due to the rising cost of energy and the decreasing grade of mined laterites, the pyrometallurgical treatment is economically marginal. For this reason, alternative treatment processes are currently under investigation. Potential applicability of hydrometallurgical treatment, using either H2SO4 or HCl, under atmospheric pressure conditions, for Ni and Co extraction from two low grade laterite ores, was examined in the present work. The two samples were selected to represent the different mineralogical composition of the saprolitic and limonitic ore deposits of the Greek laterites. The investigated parameters were temperature (65–90 °C), acid concentration (1–4 N) and solid to liquid ratio (10–30% w/v). The results indicated that HCl was more efficient than H2SO4 for the treatment of the saprolitic ore; Ni and Co extractions were very high for both elements, up to 98% and 96% respectively, while H2SO4 could leach efficiently Ni, up to 100%, but extracted only 34% of Co. Hydrochloric acid was also more efficient for the treatment of the limonitic ore, with Ni and Co extractions up to 98.3% and 87.6% respectively. With H2SO4 the maximum extractions were 71.3% for Ni and 52.1% for Co.

By John W. Lund

The Geo-Heat Center has been investigating the utilization of waste silica from the Cerro Prieto geothermal field for several years. The main objectives of the research were to com-bine silica with various additives to (1) form bricks for low cost housing, and (2) to produce a suitable road surfacing material. The various additives that were tested included hydrated lime, portland cement, plastic fibers, asphalt cement and emulsified asphalt. The silica-cement combination produced the strongest bricks and had the best weather resistance, whereas, the silica-lime combination produced the bricks with the lowest thermal conductivity and specific gravity density. The addition of plastic fibers to the silica-lime mixture improved both strength and weather resistance. The combination of asphalt and silica is not suitable as a road surfacing material, however, silica-cement appears promising.

Jan 1, 2006

By G. Granata

In this work, we studied the recovery of copper from AMD by cementation with iron powder. To control the size of copper particles within the nanoscale range, we tested the use of the anionic surfactant sodium dodecyl sulfate (SDS). We tested three concentration levels (0.2, 0.4 and 0.6 M) and temperatures (25, 50 and 75 °C). The activation energy of cementation was also assessed by fitting the experimental data with the Arrhenius equation. Under all investigated conditions, the cementation reaction was found to be a diffusion-controlled process. Without surfactant, the activation energy was 19.9 kJ/mol. In the presence of SDS the activation energy increased up to about 35 kJ/mol. With or without SDS, the particle size of the copper product was strongly affected by the cementation temperature. Without SDS, the cemented product aggregated into micro-sized clusters of about 15 μm at 25 °C, 2–3 μm at 50 °C and 1 μm at 75 °C. The addition of SDS resulted in a dramatic decrease of copper particle size up down to the nanoscale range. Under the best operating conditions, the particle size of copper was <100 nm.

By C. P. Snyman

Three independent methods of coal classification can be distinguished, namely on the basis of grade, type and rank. The latter two can be determined accurately and unambiguously only by means of microscopical techniques. These three independent variables affect all the coal properties and therefore also the technological behaviour of a particular coal. The influence of the inorganic constituents of coal on the fusibility of the ash and on the length of the slag, and also on fouling and slagging, is discussed. The fractionation of the ash-forming constituents during combustion and gasification of pulverised coal shows that fouling and slagging are not related directly to the fusibility and composition of ash of the coal as a whole. The results of combustion experiments using a drop furnace technique indicate that the ignition temperatures of the light volatiles in the coal, and of the formed char, as well as the burn-out time of the char are more dependent on the rank than on the type or grade of the original coal. High-ash coals, however, apparently ignite at lower temperatures and are more reactive than low-ash coals of similar type and rank. The surface properties of coal, which are important in froth flotation and oil agglomeration, correlate well with the inherent moisture content (and by inference with the heat of wetting and the calorific value) and therefore with the type and rank of the coal. In coal exploration, variations of rank offer the possibility of predicting the presence of an intrusion near the seam, thus contributing to more effective exploration and mine planning.

Jan 1, 1991

By Wei Gao, Qing-cai Liu, Cun-fang Lu, Huimin Zheng, Jian Yang, Chun-ling Yao

"Mercury in flue gas of coal-fired plants was concerned as another serious pollution when sulfur dioxide pollution was controlled now. The adsorbent made from fly ash by thermal precipitation sulfur to remove mercury in fuel gas from coal combustion plant, SEM, BET, TGA and other measurement methods were used to characterize the effect on surface morphology, sulfur distribution and specific surface. High temperature deposition furnace was applied to increase sulfur content in fly ash based adsorbents produced in lab. The study found that sulfur attached to the adsorbent surface, mesopore and microporous structure, increasing its sulfur content of adsorbent. Sulfur was filled in interspace as small molecule S2, S5, increased their surface area and enhanced their adsorption capacity. The specific surface area increased by thermal precipitation sulfur, and specific surface area which increased with increasing temperature.1. IntroductionThe mercury emission caused by human activity has accounted for 10%-30% of total mercury emission all over the world[11, and the emission from coal-fired power plant have a huge proportion of these emission caused by human activity. Active carbon microstructure and surface morphology play an important role in its adsorption capability, which offers the potential for controlling environmental pollutant, such as sewage, fuel gas, atmosphere and et al [2,31, because it is a material with high specific surface area that long been considered as an excellent adsorbent. At present, include activated carbon, fly ash, calcium-based sorbents and other novel adsorbents. The adsorption capacity and production cost were very important in the process of mercury removal by adsorbents, so the mercury removal has focus on developing adsorbents of highly-efficient. In particular, the waste of metallurgical from coal combustion and the others have a significant advantage about the cost, and they have the highly-efficient in mercury removal after modified to enhance their adsorption capacity, such as fly ash of coal-fired. Apart from specific surface area, element content, pore structure, and surface morphology of activated carbon have great effect on its adsorption ability. Compared to adsorbents without modification, active carbon impregnated with other elements, such as chlorine, sulfur, bromine and et al. had more excellent characteristics to remove specific pollutants."

Jan 1, 2011

By T. Plikas, L. H. Gunnewiek, L. Oshinowo

"Electric furnace smelting is one of the principal unit operations for ferroalloy production, and increased process intensity, improved availability, minimal maintenance and a longer campaign life are common objectives for electric furnace operation in order to obtain favourable economics of production. Furnace designers have continued to develop innovative solutions, e.g., furnace cooling systems, that have allowed these objectives to be realised and CFD modelling plays a key role in the design process. Enhanced understanding of the energy transfer process in the furnace and the ability to develop, evaluate and optimize components of the crucible design to match process requirements are the key motivators for modelling.This paper provides an overview of recent applications of CFD to the design of electric furnaces. The aim is to illustrate what can be done, and identify areas where further work is needed in this field. Examples include furnace bath simulation, crucible cooling system design, taphole design, baking of Soderberg electrodes, off-gas systems, and fume control and building ventilation. It is argued that the trend is for numerical models to become more encompassing while at the same time more accessible, and therefore further improvements in furnace design will be realised with continued and well validated modelling efforts.IntroductionOne of the main processing steps in ferroalloy production is the smelting of ore in electric furnaces. The three-electrode, AC submerged arc furnace is most prevalent method for smelting in the industry, with shielded-arc and DC plasma arc furnaces achieving limited application (1,2). Commercial furnaces range in size from a few megawatts to more than eighty megawatts of supplied power, and operate with the objective of maximising the return on capital invested. Maximising productivity and energy efficiency are two pathways to achieving this objective, through process intensification, increased availability, minimal maintenance, and increased campaign life for the furnace and associated equipment. Concurrently, the need to reduce the environmental impact of metal production by controlling the emission of particulate emissions, greenhouse gases, and other harmful by-products must also be met."

Jan 1, 2004

By C. H. Bucknam

A review of phase analysis methods used to characterize refractory gold ores is presented. Updating of assay methods using database technology, on-line instrument interfacing and response surface modeling is highlighted. The use of assay results to classify ores for metallurgical purposes is demonstrated.

Jan 1, 1987

By Pan Gu, Zhen Zhang, Jiang Diao, Bing Xie, Hongyi Li

Furnace refractories are in most cases chemically incompatible with smelter slag, which leads to a steady erosion in their thickness over time. Once too thin, refractory walls become mechanically unstable and catastrophic failure can result. Historically, external shell cooling was applied to generate a freeze lining of slag and thus prevent refractory erosion. Many modern high intensity smelting furnaces instead maintain their physical integrity by the use of internally cooled wall panels, plates or finger coolers. An initial refractory lining is often installed inside of the coolers, such that the furnace originally operates with a temperature (insulated) rather than a heat flux (freeze lined) boundary condition. This paper examines the change in slag-wall heat transfer coefficient and slag superheat as a function of process intensity. The implications of the changes in heat transfer on residual brick thickness are explored using analytical modelling.

Jan 1, 2016

By James R. Craig

The slags generated during gasification of petroleum coke are heterogeneous and con-sist of many different phases. These phases are important because their physical properties affect the operability of gasifiers and because they concentrate many elements that are present in the petroleum coke feed in only minor to trace quantities. An understanding of the chemistry and physical nature of these slag phases is necessary to predict behavior in the gasifier and in considering the ultimate use or disposal of the materials. Slags typically consist of silicate glasses, calcium-silicates, free iron-nickel metallic phases, iron sulfides, and aluminum oxide spinels enriched in iron, chromium, and vanadium. The partitioning of elements among these phases has been analyzed and will be discussed.

Jan 1, 1989

By Lee Fergusson

"The primary features of ViroMine™ Technology are introduced and applications of ViroMine™ Technology to mine site remediation and the treatment of a variety of intractable waste-streams, including a technical discussion of acid neutralizing capacity, metals binding capacity and longterm stability of results. Outcomes from four applications at high-profile international mine sites are presented: 1) the superfund site at the Gilt Edge Mine, South Dakota, USA (four years of data on the treatment of acidity, TDS and metals such as Al, Co, Fe, Mn and Zn); 2) one of Australia’s most polluted sites at King River Delta in Tasmania (treatment of TAA and TPA, and metal and metalloid contaminants such as As, Cr and Hg); 3) The Aljustrel “Aqua Forte” mine site in Portugal (high acidity, metal and metalloid contaminants such as Al, As, Cu and Zn) and 4) the Ulsan Iron Ore Mine at Ulsan, South Korea (treatment of metal and metalloid contaminants such as As, Cd and Ni).IntroductionThe commercialisation of ViroMine™ Technology has resolved some of the most intractable pollution issues associated with historic mining ventures on a global scale and has facilitated the neutralisation of Acid Rock Drainage (ARD), remediation of acidic and metal contaminated impoundments (including tailings dams) and promoted revegetation on tailings deposits and waste rock dumps. ViroMine™ Technology also enables current mining ventures to manage effluent simply and efficiently to meet increasingly stringent environmental standards and is enabling the mining sector to reconceptualise the management of mine spoil. The abilities of ViroMine™ reagents to neutralise the actual and potential acidity of sulphidic mine spoil coupled with the ability to bind metal and metalloid contaminants into non-bio-available forms are the key features delivering environmental and economic benefits to the mining sector and the broader community. Results from four projects utilising ViroMine™ Technology are presented to highlight the suitability of ViroMine™ Technology to treat all forms sulphidic mining wastes. 37"

Jan 1, 2008

By Guojun Qi

This work relates to wafer bumping technologies for flip chip packaging applications in the electronics industry. Nickel and its alloys are alternative under bump metallization (UBM) materials because of their slower reaction rates with Sn-based solder as compared to Cu-based UBMs. In this study, we compared the morphologies of the intermetallic compounds (IMC) formed between Sn-bearing solders (Sn3.5Ag and eutectic Sn-Pb) and two types of nickel- based UBMs, electroless Ni-P (EN) and sputtered nickel. Both chunky-type and needle-type of intermetallics were observed between the EN UBM and the solders. In the case of sputtered Ni UBM, there is only a layer of scallop-type intermetallics formed. The morphology change and growth kinetics of the IMC in thermal aging process were analysed. Kirkendall voids were noticed from samples of Sn3.5Ag solder vs Ni-P UBM that have undergone prolonged thermal aging at high temperature.

Jan 1, 2003

By Wanderson Silva Rodrigues, Paulo Adão Marinho dos Santos, José Antonio Silva Souza, Luis Alves Venancio, Emanuel Negrão Macedo

"1 AbstractThe production of alumina from bauxite using the Bayer process generates 0.7 to 2.0 ton of the residue known as red mud per ton of alumina. This material has no large scale current use and is usually stored. This paper shows that it can be used in a suspension with water as a gas effluent cleaner with high efficiency to remove SO2. It can substitute other materials currently used reducing the overall environmental impact and potentially reducing the cost of gas treatment.2 IntroductionThe production of millions of tons per year of alumina around the world generates from 0.7 to 2.0 ton of the residue known as red mud per ton of alumina. The vast majority of the red mud is stored in large sealed lakes. Due to the high reactivity this material is considered dangerous and currently there is no operating process capable of reuse all the material produced at any refinery. These lakes after filled of solid material eventually have the surface revegetated. In any cases they will remain as an environmental passive and need monitoring for decades. The search of industrial processes that combine the cleaning of gas effluents emission and reuse of these residues can contribute to the reduction of the overall impact of the alumina production process.The main objective of this work is to study the efficiency of the red mud as alternative raw material for the control of emissions of SO2 in combustion gases. Usually this is made through alkaline solutions of CaCO3 or NaOH in absorbing equipments like spray towers or packed column. This project main objective is to study the reaction of the SO2 with a suspension of red mud and water in order to obtain the basic parameters to design equipment capable of process this reaction on a pilot scale. With that goal compositions of red mud on spray were processed with flow of gas containing SO2 with concentration similar to the exhaust gases of the combustion process of the refineries."

Jan 1, 2011

By José Antonio, Silva Souza, Luis Alves Venancio, Emanuel Negrão Macedo, Antonio Ernandes M. Paiva

"The production of alumina from bauxite using the Bayer process generate 1.25 ton of the residue known by red mud and 460 kg of CO2 per ton of alumina.The direct use of exhaust gases from the alumina refineries to react and neutralize the bauxite residue may allow a double gain: open a wide range of new applications for bauxite residue reducing the reactivity of red mud and sequester approximately 15% or 67 kg of CO2 per ton of alumina.This paper shows the reaction of a suspension of bauxite residue-water with a simulation of the calcinator exhaust gases of the refinery. The influence of the temperature and the ratio water red mud is also analyzed.2 IntroductionThe production of millions of tons per year of alumina around the world generates around 1.25 tones of the residue known as red mud and 0.4 ton of CO2 per ton of alumina . The vast majority of the red mud is stored in large sealed lakes. Due to the high reactivity is considered dangerous and currently there is no operating process capable of reuse all the material at any refinery. These lakes after filled of solid material eventually have the surface revegetated. Otherwise will need monitoring for decades and remain as an environmental passive. The search of a industrial process that combine the reduction of the CO2 emission and the reduction the pH of the red mud opening the possibility of use in large scale in a economically viable way is the main objective of this work.The use of the exhaust gases of the refineries to neutralize the bauxite residue may allow a double gain: Open a large array of new applications for the residue with the reduction of its reactivity and sequester million of tones of CO2 plus other gases like SO2 [7] and NOx.This project main objective is to study the reaction of the CO2 with the Bayer process residue in order to obtain the basic parameters to design an equipment capable of process this reaction on a pilot scale. With this objective compositions of red mud on spray were processed with flow of gas containing CO2 at different temperatures and with concentration similar to the exhaust gases of the calcination process of the refineries. With the results, basic concepts of a pilot scale equipment were evaluated.A revision of the work already done on this type of residue were done [3, 9, 10]. Alternatives and potential barriers on chemistry and environmental fields were discussed. With the objective of industrial application the potential use of these materials were evaluated through the pH control, mass balance and x-ray diffraction."

Jan 1, 2010

By John O. Marsden

The past fifteen years have seen a number of important developments in copper hydrometallurgy, including the commercial application of biological heap leaching of secondary (chalcocite-dominant) copper ores, the commercial demonstration of chalcopyrite concentrate leaching technology using pressure leaching and biological processes, and the application of novel configurations of solution extraction circuits. Significant emphasis is now being placed on the development of effective stockpile leaching practices for primary ores (chalcopyrite and bornite-dominant mineralization). Some of these developments have been highly successful, and will pave the way for further development and commercialization. Others have been less successful. These developments are reviewed in the context of the metal price cycle and trends for the future are identified.

Jan 1, 2006

By Louis J. Mittoni

"It is well known that gas injection systems can exhibit a wide range of dynamical behaviours, ranging from linear periodic bubbling through to highly complex turbulent jetting. Recently, it has been observed that an important intermediate regime exists under certain system conditions, where the dynamics are complex in nature yet predictable for short time periods. This paper reviews the evidence to support the above hypothesis, and discusses the invariant quantitative measures such as density, return maps, Lyapunov exponent and dimension which may be used as pattern recognition features in a mOnitoring and control strategy.INTRODUCTIONThere has been a great deal of research on the submerged injection of gases into liquids. This interest is primarily due to the large number of applications in the pyrometallurgical and chemical engineering industries. Gases are typically injected into liquids to achieve goals such as heat and mass transfer, or physical mixing and agitation. Only recently though has the possibility of using the evolution of the gas dynamics as a probe to internal system conditions been raised [1, 2].At very low gas injection rates and small upstream chamber volumes, gas normally disperses in the form of stable bubbles of constant volume [3]. With increases in gas flow rate, the dynamics become more complex, bifurcating into double bubbling, multiple bubbling and complex coalescence behaviour. Irregularities measured in pressuretime series acquired upstream of the injection port under these complex conditions have usually been treated as bothersome noise or contamination to be filtered from the signal and ignored in the analysis. These irregularities, however, may contain physically interesting and useful information on the system from which they were produced if the system may be classified as deterministically chaotic [4]."

Jan 1, 1996

By Z. Zak Fang, P. Fan, S. Middlemas

"Titanium dioxide (T1O2) has been widely used as pigment in paints, paper and cosmetic products, as well as high-tech applications such as PV Cells, semiconductors, biomedical devices and air purification. T1O2 pigment is primarily produced by the high temperature chloride process, resulting in considerable CO2 emissions. A novel hydrometallurgical process for making T1O2 pigment without direct CO2 emission is investigated. The new method promises to eliminate direct CO2 emissions, consume significantly less energy, and produce minimal environmental waste. The novel process involves molten salt roasting of titania slag, with subsequent washing, leaching, solution purification, hydrolysis, calcination and post-treatment stages, resulting in high-purity anatase or rutile pigments while realizing significantly reduced environmental impacts. Pigment whiteness is critically sensitive to trace amounts of discoloring impurities such as iron and chromium. Several methods for reducing the levels of these impurities are investigated. Energy consumption and emission models are also developed.IntroductionTitanium dioxide (T1O2) is one of the most commonly used minerals in the chemical manufacturing industry. It has been commercially processed since the early 1900's, and has a wide variety of applications. Pigment is used in paints [1], plastics and paper [2], sunscreen [3], cosmetics and even as a food additive [4]. T1O2 has also been used in photovoltaic cells [5], biomedical devices [6], and in air purification [7]. T1O2 pigment has a refractive index of 2.7, which imparts a high level of opacity (and hence whiteness) to whatever material it is added [8]."

Jan 1, 2012

By Georgios Kolliopoulos

Water is a critical commodity of our generation and a key compound for the chemical and mining industries. Sustainable industrial development is directly associated with the ability to recover clean water from contaminated sources. Forward Osmosis (FO) is a low-energy footprint membrane process allowing the recovery of clean water from high salinity effluent streams. In FO, water is recovered spontaneously into a concentrated draw solution (CDS). Energy is required to separate the recovered water from the resulting dilute draw solution (DDS). In the current work, the fundamentals of the FO process and the most important aspects affecting its performance are discussed. An energy comparison of FO and conventional water recovery technologies is presented. Finally, the opportunities FO presents in the field of hydrometallurgy are analyzed.