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By Xue Yang

Even though many approaches have been proposed for automated fault detection and diagnosis of Heating Ventilation and Air Conditioning (HVAC) systems, and advanced maintenance programs, such as preventive and predictive maintenance have been applied for the systems, issuing work orders for corrective maintenance is still a reality. Currently corrective maintenance still accounts for more than 55% of all maintenance programs in average facilities in the US (DoE, 2010). Indoor air related problems are especially important among corrective maintenance work orders. This paper provides details of a case study conducted to capture the workflow that HVAC mechanics follow, their rationale in diagnosis process and the information they typically refer to while responding to indoor air related corrective maintenance work orders. The general workflow for HVAC mechanics to complete such types of work orders was summarized into 5 stages, and generic information requirements recorded from the case study were synthesized. Initial findings show two main challenges in the industry for HVAC mechanics to get access to required information, which highlights the need for a systematic approach that would enable identification of such information applicable to a given context under which a work order has been generated and provide values of required information for HVAC mechanics to do sound diagnosis through integrated data repositories.

Aug 1, 2013

By K. S. Coley, M. A. Rhamdhani, G. A. Brooks

Interfacial phenomena in high temperature reactions such as between iron alloy and slag is well documented but not fully understood. It is believed that a gradient of oxygen concentration plays an important role to the occurrence of such phenomena. This article describes the results from the continuation of the study of interfacial phenomena between Fe-Al alloy droplets and CaO-SiO2-Al2O3 slag. Materials characterization techniques involving microscopic observations, depth profiling, bulk, point analysis and were carried out. The roles of oxygen as well as other factors that contribute to the interfacial phenomena were evaluated. The results and their implications to steelmaking will be discussed.

Jan 1, 2004

By O. Alonso-Gonzalez, F. Nava-Alonso, A. Uribe-Salas, R. Pérez-Garibay, C. Jimenez-Velasco

A current problem in gold production is the presence of copper minerals which dissolve during conventional cyanidation practice. The dissolved copper causes several problems in the different stages of the process. This issue is the base for copper elimination/recovery methods such as the Sulphidization, Acidification, Recycling, and Thickening (SART) process, which is currently used in gold production plants around the world. Even though the process is well established, new challenges appear as the composition of the solution varies from ore to ore, in some circumstances affecting the performance of the SART process. This work presents a thermodynamic study and experimental tests performed to understand the role of the initial copper concentration and sulfur addition, on the efficiency of the copper removal. For a constant cyanide concentration, an increase in the initial copper concentration causes a decrease in copper removal; high sulfur/copper molar ratios favor copper removal. We demonstrated that the cuprous sulfide formed from solutions with high ionic strength, presents better sedimentation rates than solutions with less ionic strength. For solutions with low sedimentation rates, the use of some pretreatment is necessary to facilitate the sedimentation such as addition of flocculants, particle recirculation and the used ultrasonic pretreatment.

Jan 1, 2014

By H. Wotruba, K. Neubert

Dual-energy X-ray transmission (DE-XRT) imaging is known from safety luggage inspections at airports. The use of DE-XRT technology for sorting applications in the primary raw materials industry has been the subject of numerous investigations. Beside other metal ores, X-ray transmission sorting is already used for the preconcentration of tungsten ore, gold ore and coal. The applicability of DE-XRT sorting is limited to ore types where differences in metal concentrations are measurable, based on an interpretation of X-ray images. Metal contents in particles occur in large varieties in terms of concentration, grain sizes, spatial distribution and mineralogy and therefore influence the X-ray absorption. As a result, each ore has to be tested individually for its suitability for DE-XRT sorting. The objective of current research at the Department of Mineral Processing (AMR) at RWTH Aachen University is to assess parameters influencing the detectability of rare earth oxides. Two approaches were followed: (1) Practical test work, based on artificial ore samples of defined compositions and (2) Computer-based simulation of absorption features of identical particle compositions. In total, more than 300 artificial samples of various compositions and metal grades were produced and X-ray images from DE-XRT sorting were analyzed. Results from the DE-XRT sensor were put into correlation with metal grades and particle sizes, to analyze influences and limits on the detectability of rare earth oxides. In addition, a new approach was tested in which the X-ray absorption of particles of various compositions was determined based on a Monte Carlo (MCNP) simulation. During the simulation, similar compositions, as used for the artificial samples, were tested and the X-ray absorption behavior during DE-XRT sorting was determined. A comparison of results from both approaches is used to assess the applicability of the MCNP-simulation for the prediction of the X-ray attenuation behavior during DE-XRT sorting.

Jan 1, 2016

By M. Sommerfeld, U. Schwarz-Schampera, B. Friedrich, D. Friedmann

The steadily growing demand for metals and their price increase at metal exchanges make the mining and utilization of marine mineral resources like polymetallic nodules, manganese crusts or sulfide deposits in the near future a viable option to potentially increase the supply of base and precious metals. For a country with low potential to mine land-based resources like Germany, the industrial recovery of metals from marine mineral resources could lead to a decreased dependency on imports. In this study, seafloor massive sulfides from the German license area in the Indian Ocean (Kairei field, Southern Central Indian Ridge) are treated to recover copper and precious metals. The aim of the project is to demonstrate the transferability of existing metallurgical techniques to the raw material of deep-sea massive sulfides. As a starting point to process this unconventional resource, samples from the Indian Ocean are chemically analyzed and mineralogical characterized. A comparison is carried out between the samples and land-based copper resources, to highlight the potential which lies in mining the deep-sea floor. This paper will show the general possibility of applying a two-stage pyrometallurgical process, based on a concentrate smelting operation, followed by a converting operation in lab-scale to the provided samples of massive sulfides. Generated slag from the concentrate smelting and the converting operation are investigated by X-ray diffraction to determine the mineralogical composition. The two-stage pyrometallurgical process is investigated by the thermochemical modelling tool FactSageTM 7.2 to evaluate the phase distribution of relevant elements between the metal, matte, slag and gas phase. The thermochemical boundaries of the pyrometallurgical process are therefore set and the results of the thermochemical study can be used as an indicator for the efficiency of an up-scaled process and the generated amount of side-streams, which need to be further treated or circulated back into the process. INTRODUCTION Seafloor massive sulfides (SMS) are the third kind of discovered deep-sea minerals besides ferromanganese nodules and cobalt-rich ferromanganese crusts (Sharma, 2017). They occur in water depths around 250–4,000 m (Koschinsky et al., 2018). SMS are characterized by a high base metal and sulfide content. They were created by fluid circulation and hydrothermal convection over time (Han et al., 2018). Commonly, areas rich in SMS are associated with hydrothermal vent fields on the seafloor (Keith et al., 2018).

Jan 1, 2019

By H. Y. Sun, Q. Y. Tan, X. P. Niu, L. Li, Y. Jia, R. M. Ruan

During bioleaching processes of sulfide minerals, the sulfide minerals act as the natural habitats for acidophiles, of which, most are autotrophic iron and sulfur oxidizing microbes. These microbes acquire energy by oxidation of sulfide minerals, and play crucial role in bioleaching processes. In the industrial bioleaching heaps, microbial community and their activity are highly related to engineering configurations, while the optimized industrial operation can help to fast dissolution of aim minerals and acid/iron balance under optimized microbial condition. Microbial community succession and activity formation, the function of microbes to mineral dissolution, the mechanisms to promotion and inhibition of sulfide minerals oxidation, and the industrial instances for microbial community regulation were reviewed. For these instances, promoted microbial activity helped to fast pyrite oxidation for sulfuric acid generation, which realized zero sulfur acid addition to the irrigation solution in the initiation of a bioleaching heaps. High microbial activity by optimized operation parameters improved Cu leaching efficiency during the heap bioleaching process. And also by inhibition of microbial activity, especially the iron oxidizing microbes, the excessive pyrite oxidation can be inhibited, which helped to the acid/iron balance during heap bioleaching. INTRODUCTION Around the world, high grade copper ore are exploited, while barely new high-grade deposits are succeeded, the copper grade of ore deposit is constantly decreasing. The increasing copper demands worldwide requests to process these low-grade ore deposits. Processing of low-grade ores are not economical by usual extraction processes. Heap leaching is a cheaper process for recovery of low-grade ores, and has been applied to extract valuable metals from sulfide minerals worldwide, such as copper, gold, uranium and nickel (Gericke et al., 2009). Heap leaching process has greatly decreased the economic grade and expanded the recoverable ore reserve worldwide (Brierley, 2008). It is usually carried out in the open environments, and could process huge amount of ore (usually in millions of tonnes in one reactor) in the heap reactor (Gericke et al., 2009). For copper sulfide, especially the secondary copper sulfides, heap (dump) bioleaching is successfully applied. Heap bioleaching process is cost saving, and sometimes can be achieved without adding chemical into heaps, by microbial fixing of the atmospheric N2 and CO2, and generating oxidant Fe3+ and sulfuric acid in heaps from oxidation of sulfide minerals. Also heap bioleaching is environment friendly by cycling use of the leaching solution, and without exhaust emission.

Jan 1, 2019

By Robert Cameron, Colin Ashton, John MacNeil, Leo Piciacchia

"The in pit dam construction and utilities relocation, known as the East Mine Corridor Relocation (EMCR) project, was developed to extend the life of the east side of the Base Mine pit by two veal's. This will result in the recovery of an additional 80 million barrels of oil and delay expenditures associated with the opening of the North Mine by two years. To accomplish this, a large in pit earth structure was required to provide a new embankment foundation for relocating a public highway, four powerlines, a natural gas back-up pipeline, a substation, and a conveyor train. This structure would also he required as a temporary dam 10 contain mature fine tails on the west side until mining is completed in the east mine corridor area, that will then be filled with fluid.The in pit dam, known as The Highway Berm, is 2.5 km long, 63 m high and has 42 million m3 of engineered soil added to the already existing end-dumped soil volumes. To complete the design and construction of a structure of this magnitude, in the very short time frame of two-and-a-half years, presented many new challenges. The main challenges faced were: designing while construction was ongoing; designing without the use of clay cores or sand filters; using relatively non-select overburden material; proper dewatering and base preparation; changing from construction of 50 m high spoil piles to a high specification construction operation; compacting lifts with heavy haulers; constructing during the winter; and monitoring movement of the structure with satellites."

Jan 1, 1995

By Bétournay. M. C.

Advantages ?Safety ?Health ?Rapid, continuous development, productivity ?Stope dilution reduction Disadvantages ?High cost and long time for equipment development ?Hard rock mining condition limitations ?Size of equipment ?Equipment set-up time, down time ?Performance does not meet financial return targets ?Drill and blast retains advantage in cost, productivity, capital investment, application flexibility ?Stress accumulation issues in deep mining, ground support and material handling issues in weaker rock

May 1, 2009

By K. A. Foxford, D. A. Polya, R. P. B. Hebblethwaite

"A variety of techniques for interpreting systems of mineralized echelon veins is discussed using examples from Panasqueira and SW England. As aids for exploration and mine planning, and as a tool for ore reserve evaluation, particular emphasis is placed upon establishing vein morphology in the third dimension, and upon understanding vein dilation and propagation histories. Special attention is also placed upon investigating vein thickness and spacing relationships, and upon understanding vein segmentation. The relevant data for these techniques are all readily obtainable from stope and core sources.The vein systems described were produced in host-rock sequences that underwent incremental dilation in response to fluid overpressures, and individual veins display evidence for mineral infilling synchronous with their propagation. Echelon vein geometries resemble those reported from igneous dikes and sills: vein walls are stepped and veins are divided into segments arranged in echelons. Changes in vein geometry, from arrays to composite structures, reflect both the evolution of the vein system with time, and the changes occurring between the margins (arrays) and core (composite structures) of the system. These characteristic morphologies can be used to infer vein propagation and fluid injection trends, proximity of neighboring veins, and the shape of the system as a whole. The techniques are applicable to systems of echelon veins produced under tensile conditions in rocks where faults were absent at the time of vein formation, and where subsequent deformation has been minimal. Further work is required to assess the application to echelon vein systems formed within more complex tectonic regimes."

Jan 1, 1995

By A. Burkert, A. E. Hajj

"An information system has been developed for the use of companies considering developing a new mine which may be liable to secondary sulphide ignitions or by existing operations. The system uses the Comdale X expert system to analyze information about a particular mine. The system will indicate whether the mine is likely to experience ignitions and what precautions can be taken to reduce or prevent their occurrence. The advantage of an information system using expert system and artificial intelligence principles is that it can recommend action when there is an incomplete knowledge of all the system parameters. By interrogation of the user it can determine the state of knowledge and react accordingly. It is considered that such systems could be of significant use in mine planning for new and existing properties, especially where operators have limited expertise regarding secondary sulphide ignitions. IntroductionSulphide ignitions occur in the underground mines of several countries, including Australia, Canada, Finland, South Africa and the United States of America (1·3) and there has been a significant increase in their number and severity over the last decade(2.4). The basic causes of such ignitions are not well understood and man incidents are not reported or documented.Sulphide ignitions can pose a serious threat to the health and safety of mine workers and to the cost and efficiency of the mining operation (1-5). Byberg(6) described the three major problems associated with sulphide ignitions as:1. the force of the initial explosion can endanger workers and equipment;2. the intense heat of the ignition's flame front can endanger workers and equipment and may also ignite combustible material resulting in mine fires; and3. the sulphur dioxide produced by the ignition may be of such quantity and concentration to endanger workers, as was tragically demonstrated at Geco. In this incident in October 1985, a worker was killed at a position 2400 metres from the ignition point of a sulphide ignition at Manitouwadge, Ontario."

Jan 1, 1994

By H. L. Gibson, T. N. Setterfield, J. J. Watkins, R. W. Hodder

"Abstract - The McDougall-Despina fault set in the Noranda district of northwestern Quebec defines the eastern margin of the Despina cauldron, nested within the district-scale Noranda cauldron. The faults are stratabound in that they displace stratigraphy of the cauldron fill, but do not off-set the cauldron cover. The faults are occupied by dikes that acted as eruptive centers to volcanic members of the cauldron-filling sequence. Measurable displacement across the McDougall-Despina fault set is greater than 750 m, and coincident with post-cauldron volcanism. Feeder dikes cross-cut each other and are typically depleted in Na2O and CaO, and enriched in MgO, K2O, Fe2O3 and MnO relative to fresh flows. Economic and subeconomic massive sulfide deposits occur adjacent to the McDougall-Despina fault set at different levels over a stratigraphic thickness of 3000 m. These include the Corbet deposit, the subeconomic D-68 Zone deposits, and the subeconomic stringer zones of South Rusty Hill and Bedford Hill. Numerous copper occurrences and abundant hydrothermal alteration occur in and immediately adjacent to the fault set.The McDougall, Despina, and adjacent, parallel, ancillary faults define a synvolcanic fault set which controlled the location of magmatism, hydrothermal alteration and mineral deposition during the early evolution of the Noranda cauldron. Significant sulfide mineral deposition commonly occurred in proximity to the intersection of the McDougall-Despina fault set with northeast-trending synvolcanic faults. Recognition of synvolcanic faults is therefore a major objective of exploration programs for volcanic-associated massive sulfide deposits."

Jan 1, 1995

By A. B. Parsons, P. G. Howes

"This article discusses how recent changes in the federal and Quebec .income tax laws have contributed to an improved investment climate for mineral exploration in the Province of Quebec. Individual investors who are resident in Quebec and who are in the highest tax bracket (1984-60.4% marginal rate) may obtain tax benefits that result in only nine cents of each invested dollar being at risk.IntroductionIn a recent submission by the Mining Association of Canada to the Royal Commission on the Economic Union, it was stated that the mining industry ""is no longer discovering and opening new mines at rates sufficient to offset the depletion of existing orebodies and to maintain pre sent output"". With world metal prices still in a depressed state following the prolonged 1981-82 recession, moreover, the continuing success of Canadian mining in world markets will depend on this country's ability to compete in a new environment characterized by subsidized Third World production . For the most part, this new competitive environment will encourage the development of cost-efficient mines that are better equipped to withstand the troughs and valleys of international metals prices."

Jan 1, 1984

By H. L. Gibson, T. N. Setterfield, J. J. Watkins, R. W. Hodder

"The McDougall-Despina fault set in the Noranda district of northwestern Quebec defines the eastern margin of the Despina cauldron, nested within the district-scale Noranda cauldron. The faults are stratabound in that they displace stratigraphy of the cauldron fill, but do not off-set the cauldron cover. The faults are occupied by dikes that acted as eruptive centers to volcanic members of the cauldron-filling sequence. Measurable displacement across the McDougall-Despina fault set is greater than 750 m, and coincident with post-cauldron volcanism. Feeder dikes cross-cut each other and are typically depleted in Na2O and CaO, and enriched in MgO, K2O, Fe2O3and MnO relative to fresh flows. Economic and subeconomic massive sulfide deposits occur adjacent to the McDougall-Despina fault set at different levels over a stratigraphic thickness of 3000 m. These include the Corbet deposit, the subeconomic D-68 Zone deposits, and the subeconomic stringer zones of South Rusty Hill and Bedford Hill. Numerous copper occurrences and abundant hydrothermal alteration occur in and immediately adjacent to the fault set.The McDougall, Despina, and adjacent, parallel, ancillary faults define a synvolcanic fault set which controlled the location of magmatism, hydrothermal alteration and mineral deposition during the early evolution of the Noranda cauldron. Significant sulfide mineral deposition commonly occurred in proximity to the intersection of the McDougall-Despina fault set with northeast-trending synvolcanic faults. Recognition of synvolcanic faults is therefore a major objective of exploration programs for volcanic-associated massive sulfide deposits."

Jan 1, 1995

By William A. Napier

The Mantaro Phosphate Property is located ~ 250 km east of Lima, Peru in the Andean altiplano near the city of Huancayo, Junin District. The Mantaro deposit is a mineralized zone of phosphatic rock currently defined by surface outcrops, trenches and drilling extending over a strike length of more than 30 km and a width of more than 5 km covering ~27,700 hectares. Mineralization is exposed as three roughly parallel exposures (?mantos?) trending in a northwest-southeast direction along the Mancaspico syncline. Estimated mineral resources1 contained in Manto 1 of the Property (4% P2O5 cut-off) as of February 21, 2010, are: Measured 5.548 million tonnes @ 10.8% P2O5 Indicated 33.975 million tonnes @ 9.9% P2O5 Measured + Indicated 39.523 million tonnes @ 10.0 % P2O5 Inferred² 376.265 million tonnes @ 9.0% P2O5 1Tonnes rounded to the nearest 1,000 and grade to 1 decimal place. 2Inferred material reported with no cut-off and an assumed grade. There is considerable potential to expand the resource base. Mantos 2 and 3 of the deposit have been geologically mapped and exhibit surface mineralization widths similar to Manto 1. Given that the deposit is of marine sedimentary origin, it is reasonable to infer that comparable grades and depth of mineralization are present within Mantos 2 and 3. Based on this assumption, the potential mineral deposits within Mantos 2 and 3 are estimated to be approximately: Manto 2 425-435 million tonnes @ 9% P2O5 Manto 3 280-290 million tonnes @ 9 % P2O5 These potential quantities and grade are conceptual in nature, there has been insufficient exploration to define a mineral resource and it is uncertain if further exploration will result in these targets being delineated as a mineral resource. However, should such conceptual resources be confirmed by trenching and drilling, the Mantaro Phosphate Property would rank as one of the most significant phosphate deposits in the world.

May 1, 2011

By P. K. Kaiser, D. D. Tannant

"A support system for large ground convergence conditions or burst-prone ground must contain holding elements (rockbolts, cable bolts, etc.) that are strong yet capable of sustaining large deformations, i.e., they must absorb as much energy as possible. Steel wire rope anchored in a borehole by a friction bolt provides these desired yield characteristics if the frictional anchorage is placed deep enough into the rockmass, i.e., in non-yielding rock or beyond the expected depth of rock ejected during a rockburst. Pull-out tests were conducted on wire ropes anchored by inflated Swellex bolts to assess the feasibility of this support concept. The test results demonstrate that a Swellex bolt generates a frictional anchorage that allows the wire rope to slide at high loads and to absorb significantly more energy than either a Swellex bolt alone, or a cement-grouted cable.The rope/friction bolt combination can be engineered to provide the desired energy absorption and allowable deformation by varying the installed lengths of the friction bolt and the rope. For yielding rope support, the contact length between the rope and Swellex bolt must be short enough to ensure that the rope can slip well before its tensile capacity is reached. A safe maximum overlap length is about one metre for the wire rope used in this testing. When used as support in the backs of drifts, a swaged button on the ropes end must be used to ultimately mobilize the full rope capacity thereby protecting against gravity-driven falls of ground."

Jan 1, 1995

By J. Bruce See

INTRODUCTION This symposium at Cu 2019 has been organised to honour and celebrate the career and achievements of Dr Phillip John Mackey, an internationally recognised expert in the production of non-ferrous metals, especially copper and nickel smelting and refining. Phillip was born in Epping, a suburb of Sydney, New South Wales, Australia on 19 April 1941 and is one of 4 children of Gilbert and Philomena (nee Bartlett) Mackey. After completing Primary School in Epping, he attended Marist Brothers High School in Eastwood, Sydney and graduated in 1957 as the Dux of the School. Phillip’s father, being on the staff of the Sydney Technical College, in Ultimo, Sydney had the opportunity in the early 1950s to meet the late Professor Sir Rupert Myers, Foundation Professor of the School of Metallurgy at the New South Wales University of Technology (later called the University of New South Wales or UNSW). Gilbert Mackey was impressed by the new young Professor of Metallurgy and encouraged his son to study metallurgy - at the time an expanding industry in post-war Australia. EDUCATION AT THE UNIVERSITY OF NEW SOUTH WALES Phillip commenced at UNSW in 1958, graduating with honours in 1963. His undergraduate education and training included a few years of part-time study while working at British Motor Corporation on sheet metal forming of car bodies. At University Phillip developed his talent for teamwork. He was a contributing writer to the University newspaper, Secretary of the UNSW Students’ Union and was active in the UNSW Metallurgical Society and co-editor in 1963 of “Metallurgical Review,” the annual journal of the UNSW Metallurgical Society. His diverse interests and curiosity about the world around him were likely nourished while at University. Upon completing his Bachelor’s degree, Phillip was awarded a Commonwealth of Australia Postgraduate Research Scholarship. He began his PhD in 1964 on the thesis topic “Studies in Heat Transfer between Dispersed Liquid Metals and Gaseous Atmospheres” working under the supervision of then Associate Professor Noel Warner, an outstanding Professor at the University. Professor Warner is now an Emeritus Professor at the University of Birmingham and is internationally respected for his pioneering theoretical and practical work on established and innovative smelting processes.

Jan 1, 2019

By Osamu Inoue, Takashi Yamashita, Takashi Ikemoto

The expansion project in Naoshima smelter and refinery to meet enhancing recycling business of E-scrap was successfully completed in 2016 to have a capacity of 110,000 tpa of E-scrap treatment. Increasing treatment of E-scrap has raised the Ni content of copper anode to 4000 ppm on average, which is double the level of 10 years ago, and to 6000 ppm or more occasionally. The tank house has refined such copper anode to copper cathode with starter sheets. Since most Ni in Copper anode dissolves in copper electrolyte, the Ni content of the electrolyte has increased to 27 g/L and more. Ni accumulated in the electrolyte has increased power consumption during the electrolytic refining of copper, although cathode quality has been controlled satisfactory so far. In order to ensure sustainable operation while growing E- scrap business, the NiSO4 process has been expanded recently so as to recover Ni in the electrolyte more and the pressurized-leaching technology will be introduced to the slime leaching process so as to enhance the capacity of slime treatment and to improve Ni recovery in the near future. INTRODUCTION In recent years, the treatment amount of E-scrap at Naoshima smelter and refinery has increased according to the growth of its recycling business as shown in Figure 1, while impurities from E-scrap have concentrated in copper anode as well. Especially, Ni content in anode has been increasing remarkably since 2012, causing to raise Ni content in the electrolyte as shown in Figure 2. The increment of Ni content in copper anode and electrolyte has adversely affected the electrorefining process, slime leaching process, and NiSO4 crystallization process at the tank house. Such severe conditions provided opportunities to redesign the tank house to establish a robust process to which more Ni is acceptable.

Jan 1, 2019

By Hamid-Reza Manouchehri

Coarse particles flotation is controlled by detachment (particle hydrophobicity and flotation cell turbulence) For composite particles (the bubble may attach to good hydrophobic region, but the expansion of the three phase line of contact is limited. Hence, the equilibrium contact angle, characteristic of the hydrophobic region, may never be attained, and the force of attachment is decreased relative to that possible for homogenous hydrophobic surfaces.

May 1, 2013

By P. A. Gonzalez Contreras

Scorodite is considered as a secondary mineral formed from the product of weathering of primary minerals by chemical or biological reactions. In the case of biological scorodite formation, microorganisms mimic and accelerate what in nature takes a very long time, i.e. biocrystallisation. The goal of the biological scorodite formation is to form very stable arsenic crystals suitable for long-term and safe disposal. The biological formation of scorodite is a novel combination of biological oxidation, biocrystallisation, and proper bioreactor design to achieve the biological formation of scorodite crystals in one step. We have explored simultaneous biological arsenic and iron oxidation at 30ºC and at 70ºC leading to arsenic-jarosite phases and scorodite, respectively. As biologically formed scorodite crystals are very stable (TCLP < 1 mg/L As (V)), the risk of arsenic toxicity is minimized when leaching takes place. This process is suitable for arsenic concentrations above 0.5 g/l As achieving up to 20 mg/l As in the effluent. This biological scorodite formation system is a selfsufficient bio-oxidation system and therefore many new applications can be explored such as reprocessing of arsenic trioxide, orpiment or calcium arsenate to scorodite crystals for a stable and safe disposal.

Jan 1, 2014

By J. G. Schofield, C. G. Tan, R. J. Ord

"Most electric furnaces in the nickel and copper smelting industries are still fitted with conventional electrode holders which consist of water-cooled electrical contact clamps and a pressure ring. The water cooling exerts a significant cooling effect on the electrode column. The importance of controlling the temperature of the Soderberg electrode paste at the contact clamp area is examined, using in-plant experience and computer simulation of the paste melting and baking process. In addition to the effect of water-cooling, the effect of other variables, including the mantle air temperature, the electrode current, the furnace freeboard temperature and the electrode slipping rate are discussed. Ways in which the variable heating conditions in the paste melting zone can be controlled are outlined.IntroductionIn most non-ferrous electric smelting operations, the breakage of Soderberg electrodes is an infrequent, isolated occurrence. Occasionally, however, a rash of breakages may be experienced on a particular furnace for what appears to be no obvious reasons. The extent of the breaks may not exhibit a uniform pattern; sometimes the break may be less than half a metre above the electrode tip; at other times it may be at or just below the roof level. The latter type of break is, of course, the most dangerous since it is closest to the non-baked, weak portion of the electrode paste column. No matter where the breaks occur, they result in abnormal furnace power, charging and tapping conditions and loss of production while the new electrode section is slipped and baked. On a six-electrode furnace, breakage on one electrode has the immediate effect of reducing the total furnace power by one-third. On a three-electrode furnace, the effect is more drastic, one half of the power being lost."

Jan 1, 1995