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By Jong-Jin Pak

The present work reports the commercialization of a recycling process of spent acid to recover molybdenum. The process consists of ammonia gas neutralization of spent acid containing molybdenum, crystallization and filtration of ammonium molybdate, roasting and hydrogen reduction of molybdic oxide to produce a commercial grade molybdenum metal powder. The mother liquor, highly nitrogeneous residual solution after the filtration of ammonium molybdate, can be utilized to produce chemical fertilizers.

Jan 1, 2006

By Jimsher N. Aneli

There are many experimental works on the investigation of temperature effect on the conductivity of polymers filled by carbon materials. However frequently the establishment of current nature in the polymer heterogeneous systems becomes difficult. This fact is explained by complexity of calculation of different physical or chemical phenomena passing in materials at variation of the temperature. Among these phenomena it must be noted some morphological changes in the structure of polymers. These changes reflex on the structure of conductive system of composites. So, it has been shown, that the character of temperature dependence of thermal noises level and conductivity of some polymers filled by carbon black essentially depend on some relaxation transition in the polymeric matrix. In this paper the effect of difference transitions in polymer matrix of filled by carbon black some polymers and rubbers have been investigated in a wide temperature range. The importance of such investigation is due to possibility of application of resistive temperature sensors based on conductive polymeric composites (CPC) to measuring technology. The experiments have been carried out in the cavity with regulation of temperature in the range 110-650K. The resistance of samples was measured by four electrodes method. The samples were obtained by hot pressing of dry mixture of powdered components at chosen temperatures, pressures and cooling time in the case of plastics and by peroxide vulcanization of the elastomers in the case of the rubbers. The samples were produced on the basis of the following thermoplastics: low density polyethylene, polytetrafluoroethylene, polycarbonate and polydimethylmethylvinilsiloxane.

Jan 1, 2006

By Torben L. Edens

Norddeutsche Affinerie is the largest copper producer in Europe. Two sites are in operation for the production of refined copper: primary copper production is located in Hamburg and secondary copper production in Lünen. A total of just under 560,000 tonnes of copper cathodes is produced annually at the two sites. Primary copper production using the flash smelter furnace has been in operation in Hamburg since 1972. Over the years, the capacity of the flash smelter has been increased in three expansion projects from 120,000 t to almost 500,000 t of anode copper p.a. The anode sector consisting of two anode furnaces and a 24 mould casting wheel still features just about the same equipment as in 1972. The paper describes the most important steps taken to optimise operation which have put NA in a position to cast meanwhile more than 500,000 t of anode copper annually with the two anode furnaces and 24 mould anode casting wheel.

Jan 1, 2006

By R. M. Beauchamp

Base metal processing operations often treat process tailings and acid mine drainage using a high density sludge (HDS) water treatment process. Lime is used in this process, which reacts with existing sulfates to form gypsum. When a recycle stream is incorporated in the process, gypsum levels in recirculating water may build up and cause high levels of gypsum supersaturation. Precipitation of gypsum from the supersaturated process water causes many problems. It is speculated that gypsum may precipitate on sulfide minerals and silica gangues in the flotation circuit, resulting in decreased selectivity and recovery. An understanding of the determinants and nature of precipitation may provide solutions to mitigate the formation of precipitates and improve flotation performance. This study showed that both sphalerite and silica exhibited gypsum- or calcium carbonate-like behavior in the respective supersaturated solutions, indicative of a coating of calcium species on the mineral particle surfaces. The addition of copper sulfate and/or potassium xanthate had little effect on the precipitation of gypsum or calcium carbonate on the mineral particles. Sodium carbonate is encouraging as a method to minimize calcium species interactions on sphalerite/silica surfaces.

Jan 1, 2006

By G. I. Karydakis

Geothermal energy is an important energy asset which can play a significant role in providing energy resources to cover energy needs of a country while it can play a primary role in a particular region where it is abundant. Greece is especially rich in geothermal energy. The collision of Euroasiatic and African plates coupled with the strong tectonic tension, particularly in north Greece, resulted in the formation of important geothermal fields of low, medium and high enthalpy. These fields are in the Aegean islands, in central and east Macedonia, in Thrace and in central Greece. This work presents and analyzes information about the drilling activity for exploration and production of geothermal fields of low, medium and high enthalpy in Greece for the past thirty years. The number and type of wells drilled together with the spatial and the yearly distribution are given. Depth data has been analyzed according to the fluid temperatures and to the geological formations. Cost data are presented and analyzed for the total number of wells drilled giving also the cost per meter drilled.

Jan 1, 2006

By André C. Zingano

The coal pillars in room-and-pillar mining method are subjected to vertical stress due to overburden rock mass and horizontal stress relieve due to entries excavation around them. Some coal mining companies are applying rock bolts and steel straps to improve the pillar strength, consequently to reducing the pillar size and increasing coal recovery. This kind of approach deserves some discussion, whether it is pillar reinforcement or just rib support. The efficiency of pillar reinforcement (or rib support) is directly related to the initial load capacity of coal pillar, the type of excavation, and the width to high ratio of the pillar. The objective of this paper is to understand the mechanism of pillar reinforcement (or rib support) using rock bolts and steel straps on pillar ribs. Numerical simulation taking into account the relations listed above. The results showed that the increase of coal pillar strength is very short, and there is no influence on improvement of load capacity of pillar. However, the rib support avoids block falling, rib failure, and displacement, reducing the pillar failure propagation into the pillar center. Keywords: coal, pillar reinforcement, room and pillar.

Jan 1, 2006

By Taner Kavas

The refractory bricks of a rotary cement furnace containing of alumina and magnesium chromite were studied in order to determine whether they could be used in the concrete production as aggregates. Three mortars were prepared by mixing 1 part cement, 3 part aggregate materials, 0.5 part water by weight and mechanical, chemical, thermomechanical and microstructural characteristics were evaluated. The compressive and bending strength of samples were determined after 2 and 28 days curing. Resistance to chemicals were established by calculating the weight gain of mortars stored in 2 % HCl solution for 1 h and 24 h. Thermomechanical characteristics were determined by measuring the compressive strength of heat treated specimens at temperatures of 400 °C, 600 °C and 800 °C. Consequently, magnesium chromite containing waste brick aggregates have given the best results.

Jan 1, 2006

By H Nikraz, E Jamieson, D Cooling

The use of red sand as fine aggregate in concrete manufacture has been investigated as well as the use of fly ash as a cement replacement. The experimental work consisted of casting various concrete mixes including a control and comparing standard properties. Properties tested included compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, water permeability, chloride diffusion, pH dependence leaching and particle morphology. The results show that the concrete strength is not significantly affected when natural sand is replaced completely with red sand. The durability tests indicated high water permeability and high chloride diffusion due to the porosity of the red sand concrete, likely due to the low slump value. Leaching tests did not exceed New South Wales EPA guidelines.

Jan 1, 2006

By John Capers

•The IME is the Safety and Security Association of the commercial explosives industry in the United States and Canada. •Founded in 1913 •Board of Governors •5 Standing committees- 1. Technical 2. Environmental Affairs 3. Legal Affairs 4. Safety & Health 5. Transportation & Distribution

Jan 1, 2006

By Guojun Ma

The entrainment of charge materials, evaporation or volatilization of elements and ejection of slag and metal by spitting or the bursting of gas bubbles are mechanisms whereby stainless steel plant dust are generated from the electric arc furnace and refining converter. TCLP and ASTM D 3987-85 tests on dust that was collected from the baghouse filter system of a South African Stainless Steel plant showed that this dust can be considered hazardous according to South African legislation, due to the high degree of Cr (VI) leachability (~13mg/l for TCLP and ~8mg/l for ASTM vs. regulation threshold of 0.05mg/l in drinking water). The dust is therefore considered to be harmful to both the environment and human health, due to its high solubility in water and carcinogenic properties. It should therefore be treated before being stockpiled or land filled. This paper consequently describes an investigation into the formation of Cr(VI)-containing stainless steel plant dust and the stabilisation thereof in a sintering process, whereby the dust was mixed with a silica-rich clay. It is postulated that Cr(VI) form when the (Mg,Fe,Mn,Cr)3O4spinel phase, CaO, Ca(OH)2 and CaF2 (all of which are present in the dust) react. This reaction was found to take place both at ambient and at high temperatures (1100°C). Stabilization of Cr(VI) in the dust could be achieved at an optimum sintering temperature of 1100°C for a 50mass% dust : 50mass% clay mixture. Chromium emission during the sintering process was found to be low, and within environmental limits.

Jan 1, 2006

By Martin Brueggemann

The Tyrone copper solution extraction and electrowinning plant was the first such facility built by Phelps Dodge Mining Company in 1984. Over the next 20 years, the aqueous flow rate capacity of the plant has been expanded from the original design of 12,000 gallons per minute (gpm) to 34,000 gpm to meet production goals in the face of declining copper grades in the leach solutions. The ability to process higher aqueous flow rates through existing equipment comes at the expense of increased organic loss through entrainment to raffinate. These losses of organic (diluent and extraction reagents) can account for up to 10 percent of the plant?s total operating costs. With the recent dramatic price increase of petroleum-based products, these operating costs due to losses are sure to increase. This paper will discuss recent improvements at the Tyrone SXEW plant that have resulted in a 40 percent reduction of organic losses. These improvements include picket fence modifications, new fence materials, organic recovery systems, and operational practices within the solution extraction process.

Jan 1, 2006

By S. Harteis, D. Dolinar

Many mining operations rely on bulkheads to provide a barrier between impounded water or slurry and active mine workings. However, bulkhead failures could cause and have caused catastrophic flooding that puts the underground workforce at risk. The National Institute for Occupational Safety and Health1 (NIOSH) in collaboration with the Mine Safety and Health Administration (MSHA) is conducting research to evaluate the adequacy of existing design practices for water and slurry bulkheads. A key component of this research effort is documentation of the performance history and design parameters for bulkheads installed in underground coal mines during the last 20+ years. This research is part of a larger effort to develop general design guidelines and procedures for constructing and maintaining bulkheads that will help to ensure their long-term structural integrity, while significantly reducing the inundation risk for miners. This paper presents the results of NIOSH’s research to identify state-of-the-art bulkhead designs, including design criteria, leakage monitoring systems, and emergency warning systems. Underground observations and evaluations of existing bulkheads suggest that the most important design factors influencing their performance are the interface of the bulkhead with the surrounding strata and the potential magnitude of the hydraulic pressure to which they may be subjected. When a bulkhead has failed, leakage has generally been through the surrounding strata or along the bulkhead/strata interface, with the failure potential along the interface increasing with hydraulic head. It was also determined that development of a monitoring program to ensure the long term structural integrity of bulkheads is an important safety consideration. Current monitoring procedures range from weekly visual inspections to constant monitoring via pressure transducers and fluid level indicators. Where possible, these devices are used in conjunction with a computer based mine monitoring system to alert mine personnel when an emergency condition exists at the bulkhead installation.

Jan 1, 2006

By Alfonso Nájera

Turbulent flow of liquid steel and its control is studied using different geometries of turbulence inhibitors. Four designs of turbulence inhibitors were characterized through experiments of tracer injection I a water model and mathematical simulations using the Reynolds Stress Model (RSM) of turbulence. Geometries included octagonal-regular, octagonal-irregular, pentagonal and squared. A layer of oil was used to model the behaviour of tundish flux during steel flow. Fluid flows in a tundish using these geometries were compared with that in a bare tundish. Experimental and simulation results indicate that the flow in the bare tundish and a tundish using turbulence inhibitors open large areas of oil due to strong shear stresses at the water-oil interface but the squared inhibitor. These phenomena are explained by the high gradient of the dissipation rate of the turbulent kinetic energy using the squared inhibitor. Using this device the kinetic energy reports a high gradient from the tundish floor to the free bath surface as compared with other geometries.

Jan 1, 2006

By Roberto Javier Santiago

This paper tries to make a study about the use of calcium carbide during the tapping in replacement of part of the aluminum used in the furnace tapping, analyzing theoretical consumptions and then transfering the practice to the plant.

Jan 1, 2006

By G. J. Hasenfus

Although theoretical and conceptual knowledge regarding the impact of horizontal stress on underground coal mining excavations have existed since at least the mid-1900s, it wasn?t until the late 1970?s that the theory and practical understanding began to mesh. Since that time, particularly over the last 25 years of this Conference, increased empirical study, as well as advances in measurement technology, computer simulation, and bolt design, has significantly improved our understanding of horizontal stress impact, and provided coal mine operators with tools to reliably predict and manage it. This paper provides a retrospective review of some of the more important horizontal stress-related advancements made during the 25 years of Conference proceedings, particularly those for predicting and controlling horizontal stress impacts within underground coal mines. Relevant and significant CONSOL experiences and studies will be presented in context, with particular attention to horizontal stress considerations for longwall faces and gateroads. The significance of horizontal stress will also be placed in context with respect to local geology and structure, ground support measures, and mining configuration, method, and sequence.

Jan 1, 2006

By J. C. Gathje

Newmont&apos;s Phoenix Project is located near Battle Mountain, Nevada and is scheduled to produce copper concentrates containing high precious metal values. High temperature pressure oxidation (PDX) of the concentrates was considered as a treatment option during process development. The metals content in Phoenix concentrates range from: 15-25% for Cu, 1-10% for Zn, 0-2% for Pb and ?27% Fe. The precious metals content of the Phoenix concentrates can range up to ?300 g/t Au and >3,000 g/t Ag. As a consequence it was necessary that any process for consideration should have the capability of recovering both the copper and precious metal values. Typically, gold can easily be leached from the autoclave discharge solids, but silver is chemically bound with the jarosite formed and cannot be directly leached. Laboratory investigations led to the development of a patented PDX process that minimizes the formation of jarosite so that the silver can be leached easily along with the gold. The process was confirmed with extensive pilot plant testing. Excellent solution extraction of copper and zinc was achieved, and both iron and lead were precipitated in the PDX residue. The process produces clean PDX discharge liquors with very low iron concentrations. As an example, conventional PDX techniques resulted in pregnant liquors containing ?5 g/L Fe. However, the Newmont process, which controls the iron and sulfate species, achieved high iron precipitation in the PDX solids and pregnant liquors containing <0.5 g/L Fe. High gold and silver recoveries were achieved by direct cyanidation of the PDX solids. This process has the added benefit of producing PDX solids that demonstrate superior settling and filtration characteristics.

Jan 1, 2006

By D. T. White

Pressure acid leaching of nickel laterite ores typically involves the production of an intermediate product that is releached and refined to pure nickel and cobalt products. BHP Billiton is developing the Ravensthorpe Nickel Project to produce up to 50,000 t/y of nickel via a mixed hydroxide intermediate, which will be refined at its Queensland Nickel (QNI) Yabulu Refinery near Townsville, Queensland. The hydroxide precipitation flowsheet has been adapted to process high magnesium ores through an atmospheric leach stage, eliminate iron(III) as jarosite and oxidise iron(II) during neutralisation. The neutralisation conditions are controlled to precipitate aluminium, chromium and silicon, and to ensure good solid-liquid separation. Soluble impurities such as magnesium are purged with the tailings stream and will be managed over the long term by crystallisation in evaporation ponds.

Jan 1, 2006

By Patrick R. Atkins

Energy issues will have increasing impacts on decision making in all facets of society over the next few decades. Industrial users of energy and producers of products that affect energy use must be fully aware of the implications of their processes and products on the energy situation. This paper describes a model that has been developed for the aluminum industry that allows scenarios to be evaluated to gain improved understanding of possible implications for our businesses. A brief overview of the model is provided.

Jan 1, 2006

By Simon Lekakh

Direct reduction of Cu,Ni,W,VandMo oxides from various industrial wastes the melting of iron and steel in different furnaces was studied by thermodynamic computation and experimental methods. Thermodynamics was used to compute the final partition of the alloying additions between iron-carbon melts and oxides contained in the slag. It was shown that the sequence of the reduction reactions depended on the melt composition as well as temperature. Kinetic factors limited recovery in induction melting, while experimentally measured final partition coefficients were close to equilibrium during EAF melting. The possibility of the partial substitution of expensive ferroalloys, by different industrial wastes containing nonferrous oxides, was evaluated in foundry and mini-mill conditions.

Jan 1, 2006

By Ilkka V. Kojo

This paper gives an overview of the primary copper smelting business during the years of flash Smelting in the light of various projects taking into account the sustainability of copper production. Also the future challenges of copper smelting are addressed with special emphasis on the environment. Flash Smelting connected with either Peirce-Smith converting or Flash Converting offers the most economical and environmentally friendly alternatives for the smelting of normal and lean copper concentrates. For rich copper concentrates the feasibility of Outokumpu Direct Blister Flash smelting is, understandably, beyond compare. When the total investment costs for building a smelter and acid plant are considered, it is clear that Flash Smelting is the more feasible option compared to bath smelting. Reduction of equipment and operating cost is further achieved by the LUREC-process developed by Outokumpu Technology for operating plants with SO2-contents up to 25 % by volume. As an example the Kennecott-Outokumpu Flash Converting Furnace (FCF) has been in operation at Kennecott Utah Copper for 10 years and has achieved excellent results both environmentally and production vice. The FCF treats the entire output of the Kennecott Flash Smelting Furnace and has excess converting capacity. Furnace life, initially projected at two to three years, is now projected to be more than 5 years. It is likely the life will be essentially the same as a well-operated Flash Smelting furnace.

Jan 1, 2006