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By Matthias Schnitzler, Herbert Pfeifer, Ralf Bolling

"To transform metals high temperatures are usually needed. A fast and efficient heating can reduce the C02 emitted. The fastest way to heat metals is called direct flame impingement (DFI). The flame impinges upon the item being heated. For this method it is important to know the shape and length of the flame. Laser-induced fluorescence (LIF) technology allows measurements of a two-dimensional field without influencing the reaction or the flow. Commonly used is the measurement of OH-radicals, an indicator of the reaction zone.In the presented study measurements of a turbulent diffusion flame are shown. The position of the reaction zone and the influence of the distance between the item being heated and the burner are investigated. Conventional measurements and LIP-measurements are compared and the potential of DFI to increase the efficiency of heating metals is discussed.IntroductionDuring industrial heating processes a fast and efficient heating technology is required. Two important aspects are the NOx emission and the energy efficiency. The direct flame impingement (DFI) technology has the highest heat transfer rate possible with a gas/air flame. The turbulent high velocity flame jet impinges upon the item being is heated [ 1]. Due to the high heat transfer rate furnace and exhaust gas temperatures are lower. Therefore the energy efficiency is increased and the amount of NOx emitted is reduced.Hydroxyl- (OH-) radicals are an intermediate product that is generated during the combustion of hydrocarbons [2]. They are commonly considered as an indicator for the reaction zone and position of heat release. Figure 1 shows the hydroxyl-mole fraction in dependence of the distance along the gas flow. The figure clearly shows how fast the OH-concentration increases in the reaction zone. Figure 1 also shows that OH-radicals are present in the post combustion region, however in smaller concentration [3].The laser-induced fluorescence technology serves to measure the spatial distribution of OH-radicals in a two dimensional cross-section area of the flame. Therefore the flame dimensions and location can be determined with high spatial resolution without influencing the flow or the reaction [ 4,5]."

Jan 1, 2012

By Dean David

The evaluation of a new mineral sands prospect with unusual characteristics is described, The heavy minerals are very fine grained, have comparatively low average specific gravity (3.6) and are altered. Poor performance by conventional processing techniques made it necessary to trace the response of the major minerals during the separation processes, QEM*SEM® was used to quantify mineral volumetric abundances and mineral locking in magnetic and gravity separation products.

Jan 1, 1989

By Peng Fan

Nitride capacity is usually employed as the measure of slag?s ability to remove nitrogen from liquid metal, since nitrogen distribution ratio between slag and metal can be calculated from nitride capacity provided that the value of oxygen activity in liquid metal is available. However, during liquid metal refining processes, oxygen activity in liquid metal is usually unknown and thus it is impossible to get nitrogen distribution ratio from nitride capacity under this usual condition. In this paper, thermodynamic analysis indicates that the activity coefficient of nitride in slag can be used to measure slag?s ability to remove nitrogen from liquid metal, because nitrogen distribution ratio between slag and metal can be calculated from the activity coefficient of nitride in slag provided that the content of oxygen potential controlling element like Al in liquid metal is available. Review of reported nitrogen removal studies and our recent study has verified that for a given Al content in metal, the lower the AlN activity coefficient in slag is, the higher the nitrogen distribution ratio. Titanium monoxide based slag has been found to be much more effective to remove nitrogen than other slags. Since Al content in liquid metal is usually available during liquid metal refining processes, AlN seems to be a better measure of slag?s ability to remove nitrogen from liquid metal.

Jan 1, 2006

By R. Y. Wan

Thiocyanate was evaluated for gold recovery from low-grade refractory gold ores following biooxidation for an acidic heap leaching approach. One of the important features in using thiocyanate is that the leaching can be performed in acidic media, thus avoiding problems related to neutralization and material handling as leaching with alkaline cyanide. Also, the acidic leaching enables the use of ferric ion or bioleach solution as oxidants. In this study, Newmont-Nevada low-grade refractory sulfidic ore was biooxidized in columns at a particle size of 100% passing 102 mm. Thiocyanate leach on the biooxidized ore sample was performed on both ground samples in pulps and coarse material in columns using ferric ion as an oxidant. The variables of thiocyanate and ferric ion concentrations were compared for effect on leaching. Thiocyanate leach results are encouraging and indicate potential for development of a practical process. Gold extractions by thiocyanate are comparable to cyanide leach. Thiocyanate consumption was higher than cyanide, but was in an acceptable level.

Jan 1, 2003

By Kimio Itagaki

As a fundamental study for smelting the copper matte with high contents of arsenic and antimony in a strongly reducing condition, phase relations between the liquid matte and copper-rich alloy phases in the Cu-Fe-S-As or -Sb quaternary system and between the liquid matte and iron-rich alloy phases in the Cu-Fe-S-As or -Sb system saturated with carbon were determined at 1473 K by a quenching method. Activities of arsenic and antimony in these systems were also measured at 1473K by Knudsen cell-mass spectrometry. Furthermore, distribution ratios of silver, gold and platinum between the liquid matte and copper-rich or iron-rich alloy phases were determined in relation to the arsenic or antimony content in the systems. On the basis of these data, the elimination of arsenic and antimony from the matte to the iron-rich alloy (speiss) and the recovery of precious metals in reduction smelting of the copper matte were evaluated. It was suggested that the addition of pig iron to make a strongly reducing condition and form the iron-rich alloy, which is fluid at smelting temperatures, will be useful for fixing arsenic in the speiss.

Jan 1, 2006

By Jafar Safarian

A new kinetic modelling technique has been applied to study the rate of MnO reduction from slags by dissolved carbon in liquid iron. Based on a consideration of the fundamental reaction kinetics, a general differential equation for the slag reduction process has been formulated, which then is solved analytically for certain special cases. By re-writing the solutions in a dimensionless form the poorly known kinetic constants are eliminated, which makes the model both flexible and applicable to a wide range of experimental conditions. For example, changes in process parameters such as temperature, metal composition, slag composition, gas composition can readily be captured along with variations in the crucible geometry. Based on a comparison with a series of experimental reduction curves being reported in the literature, it is concluded that the predictive power of the model is surprisingly good, yielding outputs that are both reliable and physically reasonable. An attractive feature of the model is that it provides an alternative way of calculating the activation energies from experimental reductions curves. For example, it suggests that the activation energy for the reduction of MnO by dissolved carbon in liquid iron is about 90 kJ/mol, which is different from the previously reported activation energies. The model also suggests that the crucible geometry, which affects both slag the volume and the resulting slag/metal interfacial area, has a significant influence on the overall reduction kinetics. This design parameter is a key to further optimisation of the process on an industrial scale.

Jan 1, 2006

By A. Siegmund, R. D. Prengaman

Lead anodes used in zinc electrowinning generally contain 0.5 - 1.0 % silver to reduce the rate of corrosion over the service life. For good quality zinc, the cathodes must contain less than 10 ppm lead. In order to reduce the lead contamination of the cathode, the lead anode must become coated with a protective layer of Pb02/Mn02. The formation of this layer may take as long as 30 - 60 days, during which time zinc production is substantially reduced and the cathodes are contaminated with lead. To improve the mechanical properties of Pb-Ag-anodes alloying elements such as calcium, strontium, barium and others are added. The production of cast lead-silver or lead-silver-calcium anodes often results in the formation of numerous holes, voids or laps in the anode surface that can initiate localized internal corrosion. Based on the experience as the major supplier of rolled anodes for copper electrowinning, RSR Technologies has developed an improved anode for zinc electrowinning. The anode consists of a rolled Pb- Ag-Ca-alloy with a controlled surface grain structure. It forms an adherent protective oxide coating within 2 - 3 days when placed in an electrowinning cell. The preferred calcium and silver contents of the alloy are 0.03 - 0.08 % and 0.3 - 0.4%, respectively. Rolling sheets significantly reduces the presence of internal porosity or laps. The lack of defects results in long anode life. The rolling also produces a uniform grain structure to which the corrosion product readily adheres, thus significantly reducing the conditioning period.

Jan 1, 2000

By Yasumasa Hattori

Fluid flow in a flash furnace concentrate burner was investigated quantitatively in order to improve burner performance. Computational fluid dynamics was utilized for researching fluid flow in a burner port mathematically then its results were reviewed in the commercial flash furnace burner and its calculation results were found to be in good agreement with the actual measurement results. Based on those results, a mathematical fluid flow model for the Sumitomo flash furnace concentrate burner has been developed so as, to improve premixing and combustion efficiency of concentrate in the reaction shaft.

Jan 1, 2002

By G. White

Traditional atmospheres used for Aluminum annealing have been air, exothermic gas, and cryogenic purity Nitrogen. Air and exothermic gas have several problems associated with them such as surface discoloration, toxic emissions, and explosion hazards. High Oxygen levels can cause Magnesium streaking and oil staining, and therefore pure Nitrogen has been the atmosphere of choice for high quality Aluminum coils. A comparative study was made on key Aluminum alloys annealed in Nitrogen with different Oxygen concentrations to determine the effect on surface quality. The atmosphere composition inside the furnace was analyzed during the purge and heat cycle to determine its effects on purge times and exhaust emissions. The Aluminum coils after annealing were visually inspected for surface staining before and after rolling. The lab study revealed that Nitrogen with up to 1.0% Oxygen is acceptable, and did not adversely effects the surface quality or any of the other processing variables. However it isbelieved that higher Oxygen concentrations are acceptable depending on the rolling oils and alloy systems.

Jan 1, 1996

By James C. Sever

"With the advent of high energy costs and increasing concern for the environment leading to the incorporation the C02 life cycle as a criteria for the material used in a finished product, it is beneficial to analyze the plant and the process used in producing a raw material in order to identify practical, economic energy recovery opportunities. To this end a study was made of the proposed Nevada Clean Magnesium, Inc. Tami-Mosi reduction facility. Each source of waste heat is listed together with the assessment for potential co generation or direct recovery. The overall impact on energy requirement and C02 generation is provided.IntroductionHistorically metal reduction plants, large consumers of energy, do not recover waste heat. This occurred for many reasons:• Energy costs were low and the capital for a co-generation system could not be justified;• Waste heat sources contained entrained solids or liquids which would inhibit efficient energy recovery;• The exit temperature for the heat source was too low for efficient use by aaqueous Rankine cycle system.The business environment has now changed adding impetus to the recovery of energy previously discarded. Power costs have greatly increased. Global warming and the impact of carbon dioxide on the environment has become an issue which could impact the permitting of a plant. Technology improvements especially the development of a scaling environment waste heat boiler [l] and the development of the organic cycle Rankine cycle recovery system enable up to 70% energy recovery from ""low grade"" heat sources [2].With the inception of Nevada Clean Magnesium, Inc. 's (formerly Molycor Gold Corporation, Inc.)Northern Nevada Tami-Mosi project [3], an opportunity was presented to incorporate energy optimization from the initial design phase."

Jan 1, 2013

By Takao Mori

Novel rare earth boron icosahedral compounds are investigated as potential high temperature thermoelectric materials. REB50-type compounds and REB22C2N compounds were synthesized and the thermoelectric properties measured. Seebeck coefficients in excess of 200 V/K are observed at temperatures above 1000 K for the REB50-type compounds. Strikingly, n-type behavior was observed for REB22C2N. Up to now, non-doped B12 icosahedral compounds have all been p-type. The discovery of an n-type compound is extremely important in terms of the potential development of this class of compounds as viable thermoelectric materials. Low thermal conductivities of < 0.03 W/cm/K at room temperature was observed for these rare earth boron cluster compounds.

Jan 1, 2006

By N. S. Narayanan

Monazite, one of the major sources of rare earths, is normally opened by digestion with hot concentrated caustic soda solution. Caustic digestion dissolves phosphate and leaves a hydrated mixed metal oxides cake containing thorium, uranium and rare earths. By leaching this cake with hydrochloric acid at pH 3.0 to 3.2 bulk of the rare earths are preferentially removed and separated. The slurry left after removal of major portion of rare earths contains all the thorium and uranium present In the feed monazite. In addition this slurry also contains substantial quantities of rare earths. Solvent extraction tests were carried out to develop a process to separate rare earths, thorium and uranium present in the mixed chloride solution obtained by dissolving the above slurry in hydrochloric acid. Based on these tests a solvent extraction flow sheet was developed with di-2-ethyl hexyl phosphonic acid mono 2-ethyl hexyl ester as the extractant. The details of experimental work and results obtained are discussed and a flow sheet for processing monazite Incorporating the new process is suggested.

Jan 1, 1997

By Hao Deng, Hongmin Zhu, Jichao Li, Kai Huang

"Silicon and silicon carbide mixing micropowders obtained from the saw cutting industry of polycrystalline silicon ingot is separated by a simple sequential sedimentation. The Zeta potentials of the powders in the aqueous suspension are adjusted by varying the pHs with dilute acid or alkaline reagents. The dispersion and aggregation content of the microparticles is significantly influenced by pHs, and so their settlement velocity in the same hydraulic conditions are quite different, and silicon powders tend to suspend in the upper section of the suspension for its finer size and smaller density under the stronger Zeta potential repulsion force. The original content of the cutting powders with 30%wt silicon are separated into the Si-rich and SiC-rich powder respectively, and 62%wt Si-rich powder can be obtained after 4 times of sedimentation under pH = 8.0, showing the great potential for Si and SiC powder separation and recovery in a cost-effective way.IntroductionWith the fast development of photovoltaic (PV) technology these years, the market demand for the solar-grade high pure silicon material significantly increased, making the silicon recycling and recovery from the wire sawing slurry profitable and attractive[1]. Waste silicon slurry was produced in the multi-wire sawing process of a silicon ingot by using an ethylene glycol-based solution and silicon carbide abrasives as the slicing system. During this slicing process, about 30% of the silicon ingot will become the waste as the fine particles suspended in the slurry, which mainly consists of silicon kerf-loss particles, SiC fragmental particles, tiny iron fragments from the worn sawing wire and ethylene glycol-based solution [2]. The separation of above individual component is usually easy except for Si and SiC fine particles for their quite similar properties. So the biggest challenge for the effective recovery and recycling of silicon particles from the wire sawing slurry actually lies in the mutual separation of silicon and silicon carbide particles."

Jan 1, 2012

By G. Roderick Eggert

Material criticality reflects the degree to which a raw material is both necessary and subject to supply-chain risks. This study compares the criticality of selected raw materials from the differing perspectives of the manufacturing sectors of China, the European Union, Japan and the United States.

By James R. Myers

A source of clean gas containing sulfur dioxide and sufficient oxygen for conversion to sulfur trioxide is essential to the production of sulfuric acid. SO2 containing gases obtained from roasting sulfide ores are heavily contaminated with inorganic dust and volatile impurities. If not removed, these contaminants will reduce product acid quality, foul the catalyst beds and mist eliminators, and accelerate equipment corrosion. This paper reviews conventional gas cleaning systems for metallurgical acid plants, followed by a discussion of modern systems utilizing DynaWave Scrubber technology. This technology is based on a unique approach togas scrubbing that can concurrently accomplish several gas cleaning/processing tasks. Scrubbing liquid is injected into the gas stream to create a "Froth Zone". This is a region of extreme turbulence, with a very high rate of liquid surface renewal. It efficiently removes both particulate matter and gas contaminants, and is also a cost effective quenching device for gases as hot as 1250 o C.

Jan 1, 1992

By Olga A. Gomon, Alexey N. Lozhko

The technology of heat treatment for metal frequently includes multiple fast heating and cooling of the products surface. If the product is heavy-weight or long-size, its moving from a zone of cooling to a zone of heating and return require a long time. Other important condition of ensuring qualitative surface at heat treatment is intensification of cooling phase. It is known that turbulization of a flow activates heat exchange and increases efficacy of cooling without increasing volume flow rate of water. Additional difficulty is to ensure the regularity of heating and cooling on length of a product. The technology of cyclic heat treatment of rolling products, at which mobile zone of turbulent heat exchange is formed on the surface of a product, was developed and realized. The submission of water occurs through to face spray systems. Each of the systems has six long-range atomizers, which are located circularly. Two flows of water move towards one another along a surface of a product. When they collide, the right zone of turbulent heat exchange creates heat transfer in this zone of 10-15 time more intensive than on other surface of a product. The effect of moving turbulent zone on length of a product is reached by changing the proportion of volume flow rate of water, which is created by face sprays. The speed of movement for turbulent zone along a surface of a product is chosen so, that the cooling takes place on a small depth only. Then after passing the turbulent zone over a determined site of a surface, its temperature recovers fast owing to hot internal layers. The parameters of process were determined by mathematical simulation of cooling in an installation. The equations for dynamics of movement of collision point of flows, which were received this way, are interesting supplementary products of research. The experiments show that frequency of movement of turbulent zone is an important technological parameter. It defines mechanical properties of a surface and should be chosen depending on a profile of product and metal grade. The results of comparison of mechanical properties of a surface of various rolling products, which were received by developed and conventional technologies, are described in this report. Dependence of regularity of mechanical properties on frequency of movement of turbulent zone is adduced.

Jan 1, 1998

By M. Jennings

In 1987, Echo Bay discovered a major silver/gold ore body at their McCoy property in Nevada, and quickly made a decision to build a 5000 tpd mill which was expanded during the design to 7500 tpd. Since the ore reserves consisted of cyanide leachable oxide as well as sulfide, the plant flow sheet involved an oxide leach, a gravity circuit, and lead sulfide and a pyrite sulfide recovery by flotation. The paper describes the process development, equipment selection, plant design and the startup of the oxide treatment.

Jan 1, 1990

By Kenneth A. Brunk

"This address discusses how ""Mineral Processing Technology"" can play a major role in the life and profitability of a mining company. Examples of past and present technological breakthroughs and their impacts will be examined. Also, the future of processing technology will be emphasized.IntroductionThis talk will center on the role of technology as an important component of a business plan for mining companies. I'll attempt to explain how I see technology development as an underpinning of a successful mining company. We will examine an example of a technology that has resulted in a re-birth of segments of the industry, examine a technology life cycle and discuss technology as it relates to ore reserve replacement. Also, we will touch on technology in today's mining company and propose some food for thought for those designers of corporate organizations."

Jan 1, 1997

By Katsuyasu Sugawara, Takuo Sugawara, Shin-ji Abe, Tadakazu Kagami

"In order to clarify the mechanism and to obtain the fundamental data for heavy metal recovery from an incinerator ash by chlorination, pure chemical reagents, zinc oxide and lead oxide or the fly ash blended with calcium chloride and silicon dioxide were heated up to 1000°C in a nitrogen stream. Thermogravimetric curves of the samples with the chlorinating reagents indicated that solid-liquid reactions accelerated the chlorination and release of metals from the solid phase. The formation of liquid phase of calcium chloride played an important role on effective recovery of zinc and lead at lower temperatures below 800 °C. Although zinc and lead could be decreased in the incinerator ash without chlorinating reagents, addition of chlorinating· reagents enables the removal of metals in high extent· at lower temperature.IntroductionFly ash is discharged about 3,000 tons/day (about 110 million tons/year) from incinerators of municipal solid waste in Japan and mostly fly ash is disposed in landfills. Fly ash includes heavy metals e.g. zinc and lead. Since untreated fly ash caused hazardous leaching problems, Waste Disposal and Public Cleaning Law was revised in 1992, fly ash being designated 'specially controlled' general waste. Fly ash must be disposed by the following suitable, intermediate four methods: [I] Cement- Solidified Method, [2] Immobilized Chemicals Method, [3] Melting Solidified Method, [4] Acid Leaching Method, permitted by the Ministry of Health and Welfare, Japan."

Jan 1, 2000

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