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We describe a new method of characterising the effect of dissolved materials on the rate of coalescence of bubbles in aqueous media. Single bubbles were allowed to rise to meet the surface of an aqueous solution, and the time of persistence between arrival and bursting of bubble was measured as a function of solute concentration. A laser beam was placed just above the surface of the liquid, with a detector in the light path, so that any disturbance at the surface could be seen as a break in the beam. The arrival of a bubble at the surface could be detected from the behaviour of the trace on an oscilloscope, and when the bubble broke, another significant change in the signal could easily be seen. The time between disruptions was reported as the persistence time. The effect of a homologous series of n-alcohols (C1 to C8) on the persistence time was measured, in aqueous solution. It was found that with increasing concentration of a particular solute, the persistence time increased up to a point, and then declined. However the magnitude of the persistence time was found to increase with increasing numbers of carbon atoms in the molecule. Bubbles of 1, 2 and 3 mm diameter were used. Persistence time increased with increasing bubble diameter, the maximum values observed being of order 100 secs. For a given solute, the persistence (drainage) time increased with increasing bubble diameter. The concentration Cmax at which the maximum persistence time was observed, was found to be independent of the bubble size. It decreased uniformly as the carbon number increased, and was well correlated by the function y1/2 (dy /dc) -2 I dc)-2 . There was no apparent correlation with the surface excess at maximum persistence time.

Jan 1, 2006

By J. Makgatho, P. Condori, J. Winnett, Fischerm D.

"Palabora Mining Copper (PMC) has two autogenous mills that have been in operation since 1976. The mills were originally designed to treat 30 000 t/d of open cast copper ore in a closed circuit with cyclones. As the ore body went deeper the open cast method of mining was changed to block caving, a consequence of this was the dolerite content (hardest barren material) increased significantly, increasing the production rate of pebbles and thus reducing the milling capacity. In order to cope with the increased ore hardness and to increase mill capacity, a second ball milling stage and pebble crushing were incorporated to the circuit. The above actions created new challenges to the circuit operation and bottlenecks in different areas of the milling circuit.This paper reports the holistic work performed on the Palabora autogenous milling circuit including the implementation of a mill constraint control scheme, the implementation of a pebble removal system from the circuit and a new circuit configuration."

Jan 1, 2012

By J. Malone, D. Loth, J. Palmer

WMC Resources' Kalgoorlie Nickel Smelter was commissioned in 1972 at a design capacity of 30,000 tpa of contained Nickel in matte. A series of upgrades and progressive improvements have resulted in a design capacity increase to 110,000 tpa of contained Nickel in matte. The smelter sources nickel-in-concentrate from three Mine / Concentrators and supplies nickel-in-matte to WMC's Nickel Refinery and export customers. The Flash Furnace was last rebuilt in 1999, and is over halfway through the 10-year campaign target. The many modifications over the previous campaigns, including the Integrated Flash Furnace, are reviewed. Recent operation of the smelter and the development of the process during the current campaign are detailed herein. An overview of key interfaces with the Nickel Business Unit Concentrators and Refinery operations is provided.

Jan 1, 2005

By Masahiro Eguchi, Giuseppe Granata, Chiharu Tokoro, Hiroki Fukuda, Yuichiro Toba, Shungo Hobo

"Currently, large amounts of wastewater containing boron are discharged from industries like coal-fired power plants. Although coagulation-sedimentation is widely employed for their treatment, only a little consideration has been given to its mechanism. An additional problem is that the produced sludge has poor solid-liquid separation. This study is focusing on coagulation-sedimentation using magnesium, examining the mechanism and improving the solid-liquid separation. First, the co-precipitation with magnesium hydroxide was conducted against high-concentration boron wastewater with 500 mg/dm3as B. Second, in order to improve the solid-liquid separation by maintaining high reactivity, low-crystalline magnesium oxide was synthesized from magnesium carbonate by calcination at 400–700°C. It was tested as an adsorbent of boron and compared to co-precipitation with magnesium hydroxide. Co-precipitation showed high removal capacity. X-ray diffraction (XRD) of the sludge revealed the presence of other compounds besides magnesium hydroxide. This result suggests that other processes play a role other than simple adsorption on to magnesium hydroxide, and provides a plausible explanation for the observed high separability. As for the adsorption, the synthesized magnesium oxide immobilized as much or more amount of boron than co-precipitation. Furthermore, the results of fourier transform infrared spectroscopy (FT-IR) suggested the residual magnesium carbonate improved solid-liquid separability due to its poor solubility.INTRODUCTIONBoron is used in various industrial applications. In glass industry, the addition of a little amount of boron into glass products can enhance heat-resistance and chemical-resistance. Semi-conductor industry also employs boron as dopant for silicon. From these industries, large amounts of wastewater containing boron have been discharged. Additionally, coal-fired power plants have been recently discharging highly concentrated boron wastewater because the amount of boron contained in coal has been increasing due to a gradual decrease of the quality of coal. Since boron is partially proved to be toxic for animals, plants, and human beings (WHO, 1998),the guideline of the World Health Organization limit the boron concentration in drinking water to 2.4 mg/dm3(WHO, 2009).Because boron does not precipitate from solutions by simply changing the pH, the removal could be carried by operations such as adsorption or ion exchange. However, since ion exchange is an expensive operation with relatively low capacity, it is not suitable to treat the large amounts of wastewater produced by heavy industries like the coal-fired power plants. Therefore, coagulation-sedimentation method is still widely used as a suitable alternative way."

Jan 1, 2017

By Ray Mason

Marathon PGM Corporation?s PGM-Cu Project in Northwestern Ontario (Figure 1.0) serves as a case study to describe the process involved in advancing a deposit from grass roots exploration to the completion of several feasibility studies and the parallel commencement of environmental permitting. Through the following examination of historical exploration activities, it is clear that these activities are directly related to economic stimulus, mostly measured by downturns in the mineral industry. Other factors that influence the success of exploration advancing to feasibility and new mine development includes the ownership of the mineral claims, which also changes under these economic influences and the crucial role of interactions between the Company, the Crown and First Nations. The Marathon PGM-Cu deposit is hosted within the Eastern Gabbro Series of the Proterozoic Coldwell Complex, which intrudes and bisects the much older Archean Schreiber-Hemlo Greenstone Belt. The sub-circular complex has a diameter of 25 km and a surface area of 580 km2 and is the largest alkaline intrusive complex in North America (Walker et al., 1993). Mineralization at the Marathon PGM-Cu deposit is part of a very large magmatic system that consists of at least three cross-cutting intrusive olivine gabbro units that comprise the Eastern Gabbro Series of the Coldwell Complex (Figure 3.2.4-3). In order of intrusion, the three gabbroic units consist of (1) Layered Gabbro Series, (2) Layered Magnetite Olivine Cumulate (LMOC) and (3) Two Duck Lake (TDL) Gabbro. The relative size and abundance of the gabbroic units decrease in the order Layered Gabbro Series>TDL Gabbro>>LMOC. Late quartz syenite and augite syenite dikes cut all of the gabbros but form a minor component of the intrusive assemblage.

May 1, 2010

By \/eena Sahajwalla, Jonathan Dicker, Paul O'Kane, Cath Skidmore, James Dankwah, Magdalena Zaharia, Rita Khanna, David Knights, N Saha-Chaudhury, Somyote Kongkarat

Due to the inherent limitations of current methods of disposal of end of life polymeric materials, avenues are researched towards developing alternative, environmentally friendly and economic recycling processes. Different polymeric materials (i.e. rubber, high density polyethylene (HDPE) and polyethylene therephtalate (PET)), quite distinct in terms of chemical structure and composition, were considered in the present study as carbon resources in EAF steelmaking. Investigations were conducted in both laboratory and industrial scale steelmaking to assess the effectiveness of using these materials as carbon sources for slag foaming in EAF steelmaking. Slag foaming is important because it enhances furnace efficiency.

Jan 1, 2011

By C. Samuelsson, H. Ahmed, B Björkman, A. Andersson

The cost of raw material and energy is a continuing driving force towards working with increasing the recycling of ore based steelmaking residues. In Sweden no on-site sinter plants are operated at the integrated steelworks. Instead, selected residues from the plant are incorporated in a cold bonded briquette product which is recycled to the process via the blast furnace (BF). Since the BF sludge is the major bleed of zinc out of the furnace it is required to be de-zinced prior to recycling in the briquette product. In the present work landfilled BF sludge has been characterized with respect to chemical composition, particle size distribution, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The sludge was also subjected to laboratory scale hydrocyclone trials aiming at reducing the zinc content making the sludge viable for recycling. The results suggested that the sludge had been agglomerated prior to the characterization and hydrocyclone treatment. The zinc removal using the hydrocyclone was discussed.

Jan 1, 2015

By Olanrewaju A. Ojo, Xu Wang, Jian Xin Dong, Lina Zhang, Jerzy A. Szpunar

"The influence of crystallographic orientation on the pitting corrosion behavior of Ni-Fe-Cr alloy 028 was studied by a combination of X-ray diffraction (XRD), electron backscatter diffraction (EBSD), potentiodynamic polarization technique and atomic force microscopy (AFM). The results show that there is anisotropy of pitting corrosion that strongly depends on crystallographic orientation of surface planes. The distribution of pits frequency in standard stereographic triangle shows that the crystallographic planes close to {100} are more prone to pitting corrosion compared to planes of {110} and {111}. The calculation of surface energy (001) and (111) shows that the planes of high packing density of atoms have low surface energy with concomitant strong resistance to pitting corrosion. A correlation function between crystallographic orientation and pitting corrosion susceptibility suggests a method not only to predict the pitting resistance of a known textured materials, but also to improve corrosion resistance by controlling materials texture.INTRODUCTIONNickel-iron-chromium(Ni-Fe-Cr) alloys are widely used in various industries and engineering sectors due to their combination of good mechanical properties and high corrosion resistance(Hibner, 2001; Thomas, 2006; Ghosh, 2005).Ni-Fe-Cr alloy 028 (alloy 028)has such important characteristics worth mentioning. Alloy 028 contains high amounts of nickel, copper and molybdenum which improve its resistant to corrosion attack in reducing medium, and presence of high level of chromium makes it more resistant to oxidizing species. Moreover, alloy 028 is less expensive because of higher amount of iron compared to other similar alloys. Currently, alloy 028 is manufactured as evaporator tubes applied in the phosphoric acid production; production tubing and casing used in deep and sour gas wells; heat exchangers employed in nuclear power plants, and seawater-carrying piping and seawater-cooled heat exchangers (Bankiewicz, 2012; Kivisäkk, 2003; Gómez, 2003; Xian, 2012; Bellezze, 2004)"

Jan 1, 2017

By R. Shamsodini, A. Poor Zaeif Doost, H. Haji Amin Shirazi, M. R. Garmsiri

"With columns being installed in rougher section at Miduk Copper Complex, the rougher feed mainly reports to rougher-scavenger cells. To evaluate the efficiency of regrinding circuit, we conducted flotation experiments on samples of the feed and the products of the regrinding circuit. The grade difference of these products at 85% recovery was considered as the efficiency index. Results show that, with weight recovery of the rougher-scavengers the efficiency of the circuit increases. Exclusion of the rougher-scavenger concentrate from the feed to the regrinding circuit, resulted in an increase in the efficiency index from 10.12 to 17.6%.INTRODUCTIONThe flotation circuit at Miduk Copper Complex consists of five flotation columns as roughers and ten mechanical cells as rougher-scavengers. According to design criteria, 75% of the final product was expected to be produced by the rougher columns, while most of the feed consisting of liberated valuable particles is introduced into rougher-scavengers. To liberate locked particles, the rougher-scavengers concentrate is introduced into the regrinding circuit (see Figure 1 below). The regrind mill is in reversed closed circuit with a secondary hydrocyclones cluster, and the cyclone overflow is introduced into three parallel cleaner columns. Cleaners concentrate reports to concentrate thickener and the column tailings is introduced into six mechanical cleaner-scavenger cells. The cleaner-scavengers concentrate reports to the regrind circuit(Figure 1)."

Jan 1, 2012

By H. Z. Liu, J. M. Zhao, F. C. Wang

"Novel silicate-alginate composite beads containing 2-ethylhexyl phosphonic acid mono-2- ethylhexyl ester (P507) were synthesized and applied for the adsorption of Nd3+ from aqueous solutions. The adsorption amount of Nd3+ has been increased owing to the introduction of P507. The effect of equilibrium pH (pHe), the kinetic and isotherm experiments were investigated. The adsorption reaches equilibrium at 9 h and the maximum uptake capacity is up to 195.4 mg/(g dry adsorbent). The Langmuir isotherm equations are used to describe the adsorption process. Complete desorption can be realized with 0.2 M HCl within 20 min. INTRODUCTIONRare earth elements (REEs) have found various applications in different domains, such as metallurgy industry, ceramic industry, nuclear fuel control, photo-electro-magnetic functional materials owing to their unique properties. Neodymium (Nd), as a representative of all of the most valuable REEs, is widely used as catalysts, laser crystals, capacitors, rubber additives, Nd-Fe-B magnets, hydrogen storage and so on. Thus, the separation and purification of neodymium is significant. Unfortunately, Nd always coexists with other REEs and selective separation of the individual Nd from the REEs mixtures is still extremely difficult owing to their strictly similar atomic structures and chemical properties.Liquid-liquid extraction (LLE) and solid-liquid adsorption (SLA) are the most widely adopted techniques for the separation of REEs in the hydrometallurgical fields. The LLE process is well suited for large-scale continuous operation because of its inherent high capacity and fast kinetics. Nowadays, as a commercial extractant, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507) has been extensively studied for extraction and separation of REEs since it has considerably good extractability and high separation efficiency (Xu et al., 1992). SLA is one of the effective and green separation methods with some prominent advantages, such as easy regeneration of adsorbents, small footprint size, less industrial wastes, higher enrichment factors and column efficiency,rapid solid–liquid separation without emulsion and so on. Hence, the introduction of extractants with excellent performance into adsorbents will integrate the advantages of LLE and SLA (Lee et al., 2009)."

Jan 1, 2012

By A. Warczok, T. A. Utigard

"Slags from smelting of copper concentrates contains from 1 to 15% of copper. Copper is present in the form of copper or copper matte inclusions of size from 2 to 1000 micro, and as dissolved cuprous oxide. Removal of the copper requires the slag reduction, primarily reduction of magnetite and co-reduction of cuprous oxide. Thus, the kinetics of the slag reduction play an important role in copper recovery. Instantaneously, at the contact of carbon and a slag the gaseous film is formed. The magnetite and cuprous oxide reduction is going through a gaseous film, separating the slag and carbon of a coke or electrodes. The thickness of a gaseous film grows to a critical value and gas bubbles, containing CO and CO2, are created and rise up in the slag. Results of measurements of kinetic of the slag reduction with graphite showed high value of activation energy, close to the value of activation energy of Boudouard reaction. Strong temperature dependence of the reaction rate points out the thermal instability of the reacting system. It was found that the slowest process in the reduction stages determines the loop of CO and CO2 transfer and magnetite diffusion to the slag/gas film boundary. Strongly endothermic Boudouard reaction seems to cause thermal instability on the reaction surface. So, heat transfer to the reaction surface is very important. Due to low thermal conductivity of a slag the convection dominates in the heat transfer. So, any slag stirring accelerates the rate of reduction and coalescence of metallic copper or copper matte inclusions."

Jan 1, 2015

By T. Mulpeter, G. Deschênes

Sadiola Gold Mine is an open pit operation located in Mali and owned by Anglogold Ashanti Ltd, Iamgold Corporation and the State of Mali. A conventional cyanidation process (cyanidation/CIP) treats 15,000 tpd (of a mixture of oxide and sulphide ores) at an average grade of 3 g/t Au. In 2002, the increasing tonnage of sulphides caused an increase in production costs and a decrease in gold extraction (from 95% to 70-76%). Because of the short retention time of the leach circuit (18 hours) and the refractory nature of the sulphides, gold leaching kinetics are critical. A laboratory investigation was initiated to evaluate actual plant practice and identify a means of improving the gold leaching rate. The study was conducted on a "soft" sulphide gold sample containing 4.96 g/t Au, 0.4 g/t Ag, 2.5% pyrite, 1.2% arsenopyrite, and 0.2% pyrrhotite with a P80 of 74microns. Pre-leaching significantly influenced the gold leaching rate. A short pre-leach (2 hours) performed at pH 8, a DO of 8 ppm, and with 300 g/t lead nitrate added at the start or the end, produced the preferred conditions. Pre-leaching for more than 2 hours was detrimental to gold extraction. The cyanide concentration had to be maintained at 450 ppm NaCN to reach a maximum gold extraction within the retention time of the circuit. A maximum extraction of 81.3% Au was obtained in 20 hours (leach residue at 0.97 g/t Au). A high level of dissolved oxygen in the pre-leach was not of any benefit. Extension of gold leaching beyond 20 hours indicated that all leachable gold had been extracted by that time. Plant modifications were made to allow leaching of oxides and sulphides in separate circuits. Treatment of oxide ores is now performed at a higher rate. Sulphides are processed at a lower throughput, with 300 g/t lead nitrate, to allow a retention time of 22 hours. Combined throughput remains the same, and total gold recovery has increased from 76% to 80% for an additional gold production of 16,000 ounces per year.

Jan 1, 2005

By S. F. Guo, B. W. Zheng, X. L. Huang, S. W. Qi

"The study of mechanical characteristics of rock discontinuities under different shear deformation velocities is an important premise of rock slope dynamic response analysis. According to disposing and calculating the experimental results of previous research about peak shear strength of rock discontinuities under different shear deformation velocity of constant normal loading, the law of influence of shear velocity on the total friction angle is studied. Based on the research results, it can be found that the total friction angle of rock joint specimens varies in the form of negative logarithm with the variation of shear deformation velocity. It’s also indicated that the total friction angle of rock joints decreases with the increase of shear deformation velocity for rock joints of relative strong homogeneity and isotropy. However, the total friction angle of rock joints increases with the increase of shear deformation velocity for rock joints of relative strong heterogeneity and anisotropy and the latter amplitude of increase is less than the former amplitude of decrease. The physical property and microscopic geometry of rock joints play an important effect on the increase or decrease tendency and amplitude variation of total friction angle with the increase of shear deformation velocity.INTRODUCTIONThe rock slope dynamic response is largely restricted by rock discontinuities. Hence the study of dynamic characteristics of rock discontinuities, especially the dynamic shear characteristics is an important premise of rock slope dynamic response analysis (Qi et al., 2007). Seismic load is both dynamic load and cyclic load (Liu et al., 2011). Under the dynamic and cyclic shearing actions of seismic load, the rock slope which is stable under the condition of static load may slide along the rock discontinuities whose shear strength reduce and then the earthquake landslides occur. The strength degradation and deformation mechanism of rock discontinuities under the dynamic and cyclic shearing actions is one of the key problems to be solved in the work of earthquake prevention and control of engineering slope. Based on the above understanding, predecessors conduct some researches which focus on the shear behavior mechanical characteristics of rock joints under cyclic shearing actions (Plesha, 1987; Hutson & Dowding, 1990; Jing et al., 1992, 1993; Huang et al., 1993; Qiu et al., 1993; Homand et al., 2001; Lee et al., 2001; Jafari et al., 2003; Liu et al., 2011, 2013). However, there are a few researches about the mechanical characteristics of rock joints under different shear deformation velocities because of the restriction of shear apparatus. Crawford and Curran (1981) conducted a series of one-way cyclic direct shear tests on four kinds of natural rock joints under different shear deformation velocities varying from 0 to 200 mm/s. The tests showed that at low normal stresses the peak shear strength of soft rock joints exhibited an increase up to a certain velocity, after which it remained essentially constant. For rock joints of intermediate hardness, the peak shear strength was essentially independent of shear deformation velocity; whereas for hard rock joints, the peak shear strength of which showed a significant variation with the shear deformation velocity. Jafari et al. (2003) carried out a series of conventional triaxial tests on artificial rock joints of regular saw-tooth shape with axial loading rate from 0.05 mm/s to 0.4 mm/s."

Jan 1, 2015

By T. Lamb

There are many honor stories about aluminum in the marine environment and many are not based on facts, so they are myths. Myths must be addressed before progress can be made. This paper attempts to dispel the myths and state the facts. A common perception is that aluminum ships cost significantly more than steel ships. This paper illustrates that even though the cost of the aluminum structure is over 50% more than the steel structure, an "equivalent" aluminum naval ship can be built within 7% of the acquisition price of a steel ship. This is possible because of the cascading benefits of the aluminum ship's significantly lighter weight. Aluminum ships also have a life-cycle cost advantage over steel ships because of reduced maintenance and fuel cost savings.

Jan 1, 2011

By D. D. Macdonald, G. Engelhardt

The accumulation of damage due to localized corrosion [pitting, stress corrosion cracking (SCC), corrosion fatigue (CF), crevice corrosion (CC), and erosion-corrosion (EC)] in complex industrial systems, such as power plants, refineries, desalination systems, etc., poses a threat to continued safe and economic operation, primarily because of the sudden, catastrophic nature of the resulting failures. Of particular interest in managing these forms of damage is the development of robust algorithms that can be used to predict the integrated damage as a function of time and as a function of the operating conditions of the system. Because complex systems of the same design rapidly become unique, due to differences in operating histories, and because failures are rare events, there is generally insufficient data on any given system to derive reliable empirical models that capture the impact of all (or even some) of the important independent variables. Accordingly, empirical models have generally failed to provide a robust basis for predicting the accumulation of corrosion damage in complex systems under realistic operating conditions. The alternative prediction philosophy is determinism, in which the development of damage is described in terms of valid, physico-electrochemical mechanisms with the output being constrained by the natural laws. The differential damage is then integrated along the corrosion evolutionary path for the system (i.e., over the future operating "history") to yield the desired integrated damage, which is the quantity that is most useful to an operator. In this paper, we review the theory of predicting corrosion damage within the framework of Damage Function Analysis (DFA), with particular emphasis on the pitting of aluminum in chloride solutions and on the accumulation of damage from SCC in Type 304 SS components in the primary coolant circuits of Boiling Water (Nuclear) Reactors (BWRs). These cases have been selected to illustrate the various phases through which localized corrosion damage occurs.

Jan 1, 2005

By Chris Twigge-Molecey

"Over the last 50 years there has been a dramatic evolution in the metallurgical engineering field in Canada. In the 60s the field was dominated by large American and UK groups, often selling major process and equipment packages. The local content was limited to wrap around facilities and the civil and structural work. The mining and metallurgical companies had strong internal teams to lead these projects. Over the decades and business down cycles the large foreign contractors disappeared or re-structured and the mining companies largely shed their engineering and project management groups. The resulting gap was filled by a cadre of local specialist engineering companies, some of whom have grown to be world leaders in the field. The paper traces this evolution and examines the underlying causes and consequences."

Jan 1, 2015

By Euler De Souza, J. Daniel Stinnette, Julian Varaschin

"This paper outlines some of the factors that affect the airflow required for the ventilation of modern diesel-powered equipment and of electric equipment and examines how they can be applied in determining reasonable ventilation rates for Tier IV compliant diesel equipment and for electric equipment operating in mining environments. Airflow calculations for modern diesel-powered equipment and for electric equipment are more complex and must be based on a combination of factors that are unique to each mine. Methodologies for ventilation rate determinations for each case are proposed in this paper.INTRODUCTIONTraditionally, airflow requirements for production and support equipment operating in underground mines have been determined by multiplying the vehicle power by a ventilation rate that was either mandated by regulations or determined empirically from known quantities. However, in light of the drastic reductions to diesel equipment emissions mandated by the US EPA Tier IV and EURO Stage 4 regulations, there is still a great deal of uncertainty in the underground mining industry among those responsible for the ventilation of planned new mines or the expansion of current mines. The question remains, what ventilation rates should the ventilation system designer apply for modern diesel equipment?Also, given the ongoing development of grid/battery-electric equipment and active construction of fully electric mines, it has become critical to determine adequate airflow rates per brake kilowatt of electric engine power. One of the most important criteria for determining ventilation rates for electric equipment is the amount of heat they generate, as this is the most significant emission produced by electric equipment (which do not produce exhaust gases or particulates). Therefore, ventilation rates required to dissipate heat from electric equipment must be suitably determined for all electric vehicle fleets operating in underground mines."

Jan 1, 2019

By Ron Zevenhoven

In Finland one opportunity for large-scale CO2 capture, utilisation and storage (CCUS) is CO2 mineralisation, i.e. mineral carbonation. A process route under development towards industrial application involves production of magnesium hydroxide or sulphate from serpentinite rock (serpentine = 3MgO·2SiO2·2H2O), followed by conversion either in a pressurised fluidised bed (PFB) reactor, giving magnesium carbonate, or in an aqueous solution process giving magnesium hydro-magnesites. Iron present in the rock is typically obtained FeO(OH). Results obtained with these process routes and progress towards industrial demonstration is addressed, process heat integration and operation on flue gases (without CO2 pre-separation!) being key features for economic viability. A process route utilizing calcium-containing slag by-product from iron- and steelmaking under development towards large-scale application is the so-called slag2pcc concept. It converts an industrial by-product into valuable material, reduces use of natural material and streams to landfills while binding CO2 produced by the process generating the slag. Using ammonium salts, calcium is extracted from steel converter (BOF) slags and subsequently carbonated in a two-stage aqueous process (at ambient temperatures and pressures). Precipitated calcium carbonate (PCC) is produced while regenerating the ammonium salt. Process performance and scale-up while guaranteeing a certain PCC quality are presented.

Jan 1, 2015

By D. M. Maijer, S. L. Cockcroft, S. Modak, A. B. Phillion

"A comparison between hydrogen-diffusion-based micro-porosity formation and growth behaviour of two important aluminium foundry alloys, B206 (Al-Cu) and A356 (Al-Si-Mg) is presented in this paper. Specifically, the predicted pore size and pore fraction distribution of these two alloys resulting from directional solidification and identical hydrogen concentration are investigated numerically based on a model proposed by Yao et al. (2011. Met. & Mat. Tran. A. 42A, 4137–4148). This model takes into consideration the initial hydrogen content in the melt, the cooling rate, the partitioning of hydrogen between the solid and liquid phases, and the evolution in solid fraction with temperature. Due to different alloy chemistries, the activity of hydrogen in B206 and A356 are quite different, as are the solidification range and the resulting solidification microstructure. Being a primary alloy, B206 has dendritic microstructure and solidifies over nearly 135°C (505–641°C), whereas A356 contains fifty percent eutectic microstructure, and solidifies over 80°C (533–613°C). This allows a very different behaviour of micropores i.e. the effective pore radius in B206 is quite a bit lower as compared to A356, as is the pore number density. The evolution of local hydrogen concentration in liquid metal is analysed and compared for both the alloys.INTRODUCTION Over the past decades, the demand for materials with enhanced strength-to-weight ratios has significantly increased in the aerospace and automobile industries in order to improved fuel efficiency. For many automotive components, particularly shape castings, the trend is towards replacing ferrous alloys with aluminium alloys. The increase in the use of Al is primarily due to its low density, about one-third that of steel, and its relatively good strength that allows for weight reduction without reducing performance. Presently, Al-Si based alloys (e.g. A356) are the most prevalent due to their good mechanical performance in strength-to-weight ratio and excellent castability (Atwood et.al., 2000). However, superior mechanical properties can be achieved using Al-Cu alloys. For example, the alloy B206 offers a higher strength while retaining excellent ductility (Poirier et.al., 1987)."

Jan 1, 2017

By O. Neves, C. G. González Beca, M. C. Sol Pereira, H. Sousa Vale, R. A. Guedes de Carvalho, M. N. Sampaio

"As sulphide ores are usually concentrated by flotation , the material is very finely ground <37um), wet and impregnated with the chemicals used in flotation. These conditions are favourable to the development ofchemical reactions which are largely influenced by atmospheric conditions (temperature, humidity, wind, etc.) as well as by the geometry of the piles.Physical and chemical properties of a chalcopyrite concentrate were determined by laboratory tests. The knowledge of these properties was considered necessary in order to establish a correct design of the storage and handling operations of the sulphide ore concentrates obtained by flotation.The properties studied in this work were: transportable moisture limit, flowability, effects of vibration, hygroscopicity, ""caking"", chemical alterations by humidity, oxidation and self-heating (auto-ignition, dry and wet oxidation, self-heating by humidification and its prevention).INTRODUCTIONIn order that the handling and the transport of a powdered material may be carried out correctly, it is necessary to know certain physico-chemical characteristics. Transportable moisture limit (TML), apparent density (both aerated and compacted), compressibility, angle of repose, angle of spatula, cohesion and angle of slide(l-4) are characteristics (among the flowability parameters) worth knowing.Moisture content of the powdered material is fundamental, because if this is too low heavy losses will occur when the product&apos;s particle size is very small, if it is too high, separations between solid and liquid phases may occur. In the latter case, the centre of gravity of the system may change suddenly and cause accidents, mainly if transport is by sea or by river."

Jan 1, 1989