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By Jean Frenay

Bacterial leaching tests have been carried out on Portugese pyritic ores containing zinc, copper, lead and silver as valuable elements. Both indigenous and isolated strains of Thiobacillus ferrooxidans were used. During the tests the factors pH, Eh and dissolved oxygen were measured and related to the leaching activity of the bacteria. Different means to estimate or determine the real bacteria concentration were examined. The influence of nutrient media and particle size has been evaluated. The role of galvanic couples was studied by electrical linking of mineralogical samples of pyrite, sphalerite and chalcopyrite. Leach residues were examined by optical microscopy to follow the mineralogical alterations during the leaching. The results show a rather good leaching of the sphalerite. However, the dissolution of copper from chalcopyrite is much more difficult, 50 % recovery never being obtained.

Jan 1, 1985

By Ibrahim Yusufoglu, Ahmet Orkun Kalpakli, Cem Kahruman, Sedat Ilhan

"The effects of oxalic acid concentration, temperature, stirring rate and particle size on the dissolution rate of synthetically prepared calcium molybdate were investigated. Dissolution of calcium molybdate in oxalic acid solutions takes place as a series - parallel type reaction. In the first reaction step, which proceeds according to the ""Langmuir - Hinshelwood Mechanism"", calcium aqua oxalato molybdate is formed as a complex chelate intermediate product. In the second reaction step, molybdic acid is formed during the slow hydrolysis of calcium aqua oxalato molybdate, and it reacts rapidly with oxalic acid to form the polymeric hydrogen oxalate dimolybdate chelate as an end product. Activation energies were calculated as 41.4 and 49.9 kJ mol-1 for the first and zero order reactions. The fractional conversion versus time relationship can be given by the following equation.IntroductionMolybdenum is used widely in electric-electronic, metal working, aerospace and aeronautic, nuclear, glass and petrochemical industries because of its high melting temperature and resistance against chemical effects. However, the largest molybdenum consumers are the iron-steel and super alloy industries where molybdenum is used as an alloying element. Industrially important molybdenum minerals are limited to molybdenite (M0S2), powellite (CaMo04) and wulfenite (PbMo04), which are considered as primary molybdenum resources. Secondary molybdenum resources are spent catalysts and scrap [1-4].Molybdenum has been produced by pyrometallurgical processes in the past. Since it is possible to process low grade molybdenum ores and industrial wastes by hydrometallurgical processes, which are more environmentally friendly than pyrometallurgical processes, the importance of the use of hydrometallurgical processes has increased in the molybdenum production industry."

Jan 1, 2012

By Dengfu Chen, Huabiao Chen, Yunwei Huang, Mujun Long, Youguang Ma, Lintao Gui

In the current work, a three-dimensional model coupling turbulent flow, heat and solute transport was developed to investigate the solute transport and redistribution in the mold of slab continuous casting where the Reynolds number is very high and the molten steel flows strongly. The conservation equations of momentum, energy and species for a multicomponent system which includes solute element C, Si, Mn, P, S were solved with the commercial software ANSYS Fluent. The parameters used in the model are based on the actual continuous casting. The fluid flow, temperature distribution and solute elements distribution were analyzed. Results showed that negative segregation occurred near the strand surface, and the species concentration reached a peak value at the solidification front during solidification. The segregation degree of solute element S is higher than the other solute elements because of its lower equilibrium partition coefficient. The species concentration in the liquid pool is homogeneous because of the turbulent flow effect.

Jan 1, 2015

By John O. Burckle

For years, the measurement of fugitive emissions from the primary copper converter has defied all attempts based on inferential measurements, It has been concluded by virtually all investigators that the only dependable tech¬nique to measure these emissions would be to completely enclose an operating converter to permit the capture and measurement of all emissions. However, complete enclosure with a metal hood is difficult; many of the most serious fugitive emissions result during periods when the converter must be attended with crane-operated equipment. This approach would require either opening of the enclosure to permit the entry of large items of equipment or completely new methods for charging and tapping converters' The installation of the air curtain hooding system at ASARCO's Tacoma smelter has permitted a quantitative approach to the direct measurement of the fugitive for the first time. In this program, the fugitives captured by the air curtain were measured at a downstream sampling point in the exhaust side of the air curtain system during the various portions of the converter cycle. Emission factors were established for sulfur dioxide, filterable particulate (method 5), inhalable particulate, and selected trace elements.

Jan 1, 1983

By Zhong g. Shui-ping

A new type Pb-Ag (0.8wt%)-Bi (0~5.0wt %) alloy used as anode in electrowinning of zinc from sulphuric acid electrolytes was prepared. The electrochemical properties of this ternary lead alloys have been tested and compared with those of Pb-Ag (0.8wt %) anodes used in industry. Results show the anodic overpotential decreases with the increasing of Bi content in the alloys. When the content of Bi was 1.0 wt% and 5.0 wt%, the anodic overpotential is about 40?50 mV and 60?80 mV lower than that of Pb-Ag (0.8wt %) alloy, respectively. The formation of oxide layers on the surface of these alloys was traced by LSV methods and the composition of the anodic oxide layers was characterized by XRD and SEM analysis. The surface layer on the two type anodes examined is mainly composed of a?PbO2 and ß?PbO2. But different structure of the surface layer was observed, Pb-Ag (0.8wt%)-Bi (1.0wt %) has a more fine-grained structure as compared to Pb-Ag (0.8wt %). But the film on Pb-Ag (0.8wt%)-Bi (3.0wt %) alloy is rather friable, cracked and not tightly attached to the anode.

Jan 1, 2008

By Ephraim Jeya Kumari

The demand for the titanium dioxide pigments and the shortage of higher-grade titaniferous ores with low radioactivity and zircon sands worldwide has encouraged the development of new techniques for the beneficiation of lesser grade titaniferous ores. The inferior quality ores are invariably richer in radio-active and lanthanide oxides, which severely interfere with the fluidized bed chlorination reaction (FBCR), in which ultra-high purity titanium tetrachloride is distilled off for pigment manufacture. However the present beneficiation techniques require high quality ilmenite ores and are not suitable for upgrading lower grade ilmenite ores which do posses trace metals in the form of lanthanides and actinides as Al-phosphates and zirconium silicates, respectively. The presence of mineral hosts, zircon sand and monazite in ilmenite and anatase also increase in chlorine gas consumption in the FBCR and contribute to a larger volume of hazardous waste production, which must be neutralised at a significant cost before being disposed off safely. In view of the problems described for lanthanide (Ce, Nd etc) and actinide (Th, U) trace impurities in titaniferous ores, an alternative route, which is flexible and more accommodating for processing difficult ores, is discussed. In the new process, which may be used for richer grades of ores too, the ore is roasted in air with sodium carbonate below 950°C to promote the formation of water-soluble sodium ferrite and insoluble sodium titanate phases. In this investigation, the high-temperature roasting process and the ensuing hydrometallurgical leaching steps have been analysed in the context of selective separation of lanthanide and actinide minerals from the main titaniferous mineral structures. Evidences for the selective separation are presented based on the chemical (XRD, XRF, AA) and microstructural analysis (SEM, EDX, EPMA) of roasted mass and the leached product. The efficiency of selective separation is also reported based on the chemicals analysis and the particle size of the materials derived after leaching. The paper highlights the various thermodynamic aspects of reaction equilibrium in the Fe-Ti-O-Na system, and the effect of Eh-pH diagram in the determination of pH required for the better control of the removal of iron and sodium. Two different types of Ti ores, namely ilmenite and anatase, their crystal structure and the phase transformation will also be explained on the basis of wet chemical analysis, XRF, XRD, EPMA and SEM-EDX studies. The method developed examines the technological feasibility of the selective separation process.

Jan 1, 2006

By Marshall Khan

The Goodfellow Expert Furnace System Optimization Process (Goodfellow EFSOP?) is a proprietary process that uses real-time and continuous off-gas analysis, along with process monitoring to optimize the operation of electric arc furnaces (EAF) for steelmaking. With the exception of off-gas composition, dynamic process measurements within the EAF are not possible due to the harsh operating environment. The Goodfellow EFSOP? system provides a dynamic indication of the operating conditions within the EAF. Continuous measurement of furnace off-gas composition, along with other furnace operating parameters is used to elucidate the fate of chemical energy usage within the EAF including: the evolution of carbon from the molten steel bath; the in-leakage of air into the furnace; the extent of combustion above the molten steel bath and the occurrence of dangerous water-leaks from the furnace cooling system. The ability to measure the process reliably and continuously enables Techint Goodfellow Technologies Inc (TGTI) to implement dynamic process control of combustion within the electric arc furnace and to optimize the overall operation through adjustments to the EAF process based on off-gas measurement. This paper discusses the methodology and results achieved from several recent Goodfellow EFSOP? installations in South East Asia.

Jan 1, 2006

By Anita E. Lam

The thiosulfate leaching of gold generally requires the presence of a catalyst such as cupric tetraammine, Cu(NH3)42+, to obtain reasonable leaching rates and gold extractions. Unfortunately, this same catalyst that accelerates gold leaching also tends to accelerate thiosulfate oxidation to tetrathionate and other species. It is therefore imperative that a detailed understanding of the role of this catalyst and the factors affecting it is obtained. It is equally important for plant application that a method of assessing the catalyst be developed. In this work the role of the cupric tetraammine catalyst was studied using geochemical modeling for speciation prediction, thiosulfate leaching of gold ores, and chemical analyses of resulting leach solutions. It was found that the variables of pH, temperature, and the concentrations of ammonia, thiosulfate, and total copper all work in concert to affect the concentration of the cupric tetraammine species. It was also found that the presence of sufficient thiosulfate and cupric tetraammine was critical to the success of the leach.

Jan 1, 2003

By J. N. Hryn

This paper describes some of the work done in Phase 1 of a multi-year, five-phase program aimed at demonstrating the economic feasibility of producing commercial-scale quantities of commodity materials derived from salt cake residue-oxide. The amount of salt cake generated annually in the U. S. is estimated to be 510,000 tons, including 340,000 tons of residue-oxide. Used beverage can (UBC) processing accounts for the majority of residue-oxiae that could be made available for further processing into commercial products. To characterize the composition of residue-oxide. eight residue-oxide samples from various secondary processors were obtained and analyzed. Surprisingly, the composition of residue-oxide was found to be independent of source or alloy family being processed, with? the exception of slightly elevated silicon levels in 3XXand UBC residue-oxide samples. Major phases detected in the residue- oxide were? alumina, spinel, and aluminum hydroxides. Preliminary economic analyses indicated that the refractory market appears to be the best choice for high value-added products produced from residue-oxide with minimum processing. Bench-scale tests indicated that low silicon containing residue-oxide is ready to enter this market, but the elevated silicon content of UBC and 3XX residue-oxide preclude this possibility. A separation technology should 'be developed to remove silicon-containing . species from the alumina and spinel values Present in residue-oxide. This technology would then allow UBC and 3XX residue-oxides to be converted to significantly higher value-added products.

Jan 1, 1995

By Damien Wagner

To reduce the emission of greenhouse gases by the steel industry, particularly for ironmaking, the production of DRI (Direct Reduced Iron) using hydrogen as the reducing gas instead of carbon monoxide is being considered. In this context, the reduction of pure hematite by hydrogen was studied at the laboratory scale, varying the experimental conditions and observing the rate and the course of the reaction. All the reduction experiments were performed in a thermobalance and supplementary characterization methods were used like scanning and transmission electron microscopy, X-ray diffraction, and Mössbauer spectrometry. The influence of rising temperature in the range 550-900°C is to accelerate the reaction; no slowing down was observed, contrary to some literature conclusions. A series of experiments consisted in interrupting the runs before complete conversion, thus enabling the characterization of partially reduced samples. Interpretation confirms the occurrence of three successive and rather separate reduction steps, through magnetite and wustite to iron, and illustrates a clear structural evolution of the samples. Finally, the influence of the sample type was revealed comparing a regular powder, a nanopowder and a sintered sample. The regular powder proved to be the most reactive despite its larger grain size, due to a more porous final structure.

Jan 1, 2006

By Geir Wedde, Anders Sorhuus

"Vast quantities of energy are released as heat to the environment from industrial operations. Many countries target waste heat recovery to mitigate CO2 emission. Exhaust gases from industries such as primary aluminium smelting, carry a substantial portion of the waste heat generated. For a cost efficient capture of more valuable heat (higher exergy), heat exchangers should operate on the exhaust gases upstream of the gas treatment plants. Heat exchange surface would be exposed to dust laden gases with risk of fouling. Heat exchangers of innovated design and operation have overcome the potential of excessive fouling rates. Heat exchangers of the ""shell and tube"" design have been demonstrated for exhaust gases from ferroalloy as well as primary aluminium smelters. In addition to the heat recovery, gas cooling results in smaller gas treatment plants with lower costs and reduced emission. The aluminium experience is exampled in the paper.IntroductionIndustrial usage of energy continues to grow as a result of increasing volumes of production, a trend that is likely to continue in the coming decades as living standards keep rising globally. World energy consumption (Figure la) is to grow 49 % by 2035 (ref. 2010) as reported by EIA [1]. The industrial sector consumes somewhat more than 50% of the total world energy consumption predominantly the energy increased demand comes from non-OECD countries in Asia. The industrial consumption by production of metals iron and steel accounts for 14 % and for non-ferrous metals 3 % mostly for aluminium production (Figure lb). Aluminium production will be discussed in this paper as an example of an industry with large quantities of waste heat to recover"

Jan 1, 2012

By Edgar Blanco

At the Deer Trail Mine, interest in recovering noble metals from oxide ore and tailings oxide ore with 6.0/1.0 g/t Au and 200/140 g/t Ag respectively has led to metallurgic studies focused on finding an adequate treatment for these materials. Using cyanide leaching, the silver/gold recoveries from oxide ore and oxide tailings were 39%/95% and 36%/96%, respectively. Since these recoveries were less than spectacular for silver, it was decided to explore a non-cyanide leaching process that would extract silver and gold better. Based on previous research the possibility of using aqua regia in combination with sulfuric acid was evaluated. On a laboratory scale, variables such as mineralogical composition, concentration of reagents, dissolved oxygen, reaction time, pH and temperature were evaluated. Under optimal conditions it was possible to achieve >65% silver recovery and >85% gold recovery for both oxide ore and tailings.

Jan 1, 2009

By J. E. Dutrizac

Mineralogical studies were carried out on nodulated copper cathodes from three primary refineries to characterize the nodular growths and to elucidate the causes of the nodulation. Nodulation is often initiated at the surface of the starter sheet or the stainless steel plating blank, although a layer of smooth copper sometimes is deposited before nodulation commences. In some instances, the "roots" of the nodules exhibit a pronounced dendritic texture that is associated with an abundance of cavities. Slimes particles are not usually associated with these growth features which lead to a globular surface deposit. The globules sometimes develop into larger nodules, and this type of nodulation is likely caused by improper addition agent concentrations. The nodules on most cathodes, however, exhibit "roots" at the contact with the substrate that are associated with microcavities and large clusters (>40 µm) of slimes particles. The slimes constituents are commonly Ag powder, PbSO4 and Cu2(Se,Te) but not AgCu(Se,Te) or Ag,(Se,Te). The size of the slimes clusters, rather than their composition, appears to be the important factor causing the copper to grow into nodules. Tiny individual slimes particles themselves do not appear to cause cathode nodulation.

Jan 1, 1999

By Bret Boster

Facilities at Amax Gold's Sleeper Mine process some 330 kt of high grade ore and 4100 kt of low grade ore annually to produce 6.8 t of gold and 7.8 t of silver. High grade ore is processed in a conventional milling facility employing gravity concentration, CIC and CIP unit operations for gold and silver recovery. Low grade ore is processed using heap leaching and carbon adsorption methods.. Presented are the evolution and descriptions of the Sleeper processing facilities and discussions of selected' operating results.

Jan 1, 1989

By John A. Clark, Danylo Oryshchyn, Casey Carney, Stephen Gerdemann, Cathy Summers, Thomas Ochs

"Limited analysis of combustion gas streams where carbon capture is not of interest is done mainly to ascertain operation parameters. Stringent regulations on acid gases and particulates promote careful flue gas analysis. Unregulated components are typically not analyzed. Typically not more than four points (two in the boiler, and one each in the flue and the stack) are sampled. A successful oxy-fuel process with carbon capture and compression is anticipated to require as many as 12 sample points with analysis for water, nitrogen, oxygen, argon, NOx, SOx, and carbon monoxide. Carbon dioxide captured for beverages produces a high value product and the cost associated with analysis is warranted. However, carbon capture for disposal must keep all costs to a minimum. This paper will compare alternative approaches for cost-effective sampling and analysis of the carbon dioxide product streams from oxy-fuel combustion, through all stages of production through compression and pipeline/vessel delivery.IntroductionAnalysis of gases in an oxy-combustion process with carbon capture is essential to the operations of the oxy-fired boiler and the subsequent collection, compression, and purification of carbon dioxide. The process is charged with pure oxygen and not-so-pure carbon in the form of coal at the front end, generating a product of mainly carbon dioxide with traces of argon, nitrogen, sulfur compounds, nitrogen compounds, oxygen, hydrogen, and mercury. It is possible that hydrogen chloride and hydrogen sulfide may also be present in trace amounts [1]. The trace components primarily come from impurities contained in coal such as water, sulfur, nitrogen, and volatile organic compounds. Coal also contains a good deal of mineral matter that is transformed into ash during combustion, becoming particulates that can complicate the analysis regimes utilizing standard analytical equipment."

Jan 1, 2010

By L. Béjar-Gómez

The aim of this research work is to study and characterize the precipitates in structural microalloyed steel by transmission electron microscopy and analysis by low resolution. Microalloyed steel with niobium was produced by casting in an electrical induction oven of 25 Kg capacity. Carbon content in steel was less than 0.1 % and 0.036% of niobium. Steel was processed thermomechanically; reheated to 1250 °C and hot rolled on a laboratory mill to a 13.0 mm thick plate with a finish rolling temperature of 900ºC and a thickness reduction of 80% . This work shows what precipitates are present in steel, the type of precipitates and their morphology. Analysis by transmission electron microscopy of low resolution was applied to obtain the chemical analysis of precipitates and the matrix. Spectroscopy of dispersive energy (STEM - EDS) was applied to obtain the element profile of precipitates. Particles of precipitates of NbC were found; with cubic morphology and size from 70 to 130 nm, circular morphology and size from 10 to 70 nm, polygonal morphology and size from 10 to 80 nm.

Jan 1, 2006

By P. D. Nolan

Smelters operating under pollution control orders have become increasingly dependent upon the reliable operation of sulphuric acid plants and no factor affects the long term reliability of those plants more than efficient gas cleaning. The sources and characteristics of contaminants in smelter of fgases and the conventional approaches to removing these contaminants to accepted levels are discussed. New technology is described which offers advantages of lower capital cost, lower operating cost and reduced space requirements over the conventional approaches. This new technology has been developed by LAB s.a. and is licensed for metallurgical gas applications by Chemetics International Company.

Jan 1, 1983

By Laila A. Guirguis

Impurities are removed from crude phosphoric acid (57.75% P2O5) with a mixture of low and high molecular weight alcohols, one of which is hydrophilic and the other is hydrophobic i.e. methanol and hexanol. In a single stage, the phosphate values segregate to the high molecular weight alcohol fraction and the impurities segregate to the low molecular weight alcohol fraction. The optimum ratio for the extraction is found to be 0.5 part methanol, one part impure acid and four parts hexanol where an extraction percent of more than 95% is achieved. Re-extraction of the phosphate value from the solvent is obtained by 6% phosphoric acid and the different factors affecting the re-extraction process have been studied. Finally, the purified acid is concentrated under reduced pressure and passed through activated carbon column, whereas the alcohols are re-circulated. The produced phosphoric acid was found to be in good match with the international specifications of food grade quality acid. A technological flow sheet is elucidated.

Jan 1, 2006

By Ilona Johnson

United States metals and non-metallic minerals manufacturing consume about 5,000 trillion Btu annually. Various studies estimate that as much as 20 to 50 percent of this energy is lost as excess or waste heat. Recovery of waste heat can conserve energy, reduce operating costs, and lower environmental emissions. It would be valuable to quantify recoverable waste heat sources and identify the barriers that hinder its recovery. This paper provides an overview of waste heat losses specific to high temperature processes in primary metals and minerals manufacturing. It summarizes findings from a broader study conducted for the Department of Energy Industrial Technologies Program; the study evaluates energy losses, recovery practices and opportunities, and R & D needs for waste heat technology development.

Jan 1, 2008

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