Search Documents

By Mingmei Zhu, Lang Hu, Yu Wang, Hongpo Wang, Congjing Zhang

Magnetic field has a great effect on the crystallization behavior of mold flux and properties of the flux film between mold and strand, on which the surface quality of strand was deeply depended in continuous casting process. Therefore, studying the change law of the crystallization properties of mold flux in magnetic field is of great significant. In the present work, based on intensity of the applied magnetic field with the range from 0mT to 60mT, the crystallization ratio, crystal size and mineralogical phases of the flux film were discussed. The results show that crystallization ratio increases with the increasing magnetic field intensity, and the crystal size becomes bigger at the same time. The magnetic field promotes the crystallization ratio and growth speed of the crystallized grains of mold flux. However, magnetic field doesn’t change types of the mineralogical phases.

Jan 1, 2015

By Autumn Fjeld

The filling and solidification of an industrial scale composite casting has been simulated to investigate the re-melting of the outer shell material during casting. Production of a composite requires a two-step casting process which includes centrifugal casting of a hard outer shell material and subsequent conventional ingot casting of a tough core material into the shell-mold assembly. During casting of the core, a thin layer of the shell material re-melts and mixes with the core material producing a bonding layer of intermediate composition. The present numerical model employs the volume of fluid method and an enthalpy-porosity technique to couple the filling of the core material and re-melting of the shell material. The interface between the two materials is tracked and can be used as a guide to examine the extent of melting and, to some degree, mixing of the two fluids and species diffusion.

Jan 1, 2008

By Niels Verbaan

NioCorp is developing the niobium/scandium/titanium Elk Creek carbonatite deposit. The probable reserve announced by the company in 2017 indicated significant niobium (0.79% Nb2O5), titanium (2.81% TiO2), and scandium (71 g/t), and is composed predominantly of calcite, dolomite, and ankerite. Niobium is mostly (80%) contained in pyrochlore with the balance in various Fe-Nb-Ti oxides, which also host most of the titanium. Scandium is primarily deported in dolomite, with lesser quantities in pyrochlore and biotite. The process flowsheet recovers separate niobium, titanium, and scandium products. Scandium is extracted from whole ore hydrochloric acid leach solutions using solvent extraction and is further refined through a re-leach and precipitation process. Scandium leach residues are treated in a sulphuric acid sulphation process to recover separate niobium and titanium precipitates as well as to solubilize the remaining scandium. Both hydrochloric acid and sulphuric acid reagents are recycled within the flowsheet. This paper will discuss key bench and pilot test results of the niobium extraction and recovery circuits and will present a conceptual flowsheet developed by the project team for NioCorp at SGS Minerals.

By Lev Levin, Sergei Lesokhin

"The formation of titanium carbide during hot filament assisted carburizing of NiTi alloy was investigated. Phase content and morphology of the diffusion zone were examined by X-ray diffraction, X-ray microanalysis, SEM, and Auger electron spectroscopy. The growth of stable and adherent TiC film was observed. A non-planarity of interphase boundary was noticed. The applicability of the chemical diffusion approach to the analysis of the experimentally observed interface instability is discussed. A criterion, taking into account the influence of growth stresses on the stability of the flat interface, is developed by means of linear perturbation analysis.Introduction.Equiatomic intermetallic NiTi belongs to a class of materials exhibiting the shape-memory effect. The unusual property of this compound promotes its application in many fields, from aerospace technologies to medicine. The relatively high ductility ofNiTi also permits its use as a matrix material in metal-ceramic composites. The objective of this work was to investigate the possible incorporation of a ceramic material (titanium carbide) into NiTi by gas carburizing.Free energy calculations indicate the potential to obtain TiC by carburizing Ni-Ti binary phases. The main obstacle to such a process is the high affinity of titanium to oxygen. At moderate temperatures the formation of TiC is preferable to titanium oxidation only if the partial pressure of oxygen is extremely low [1]. This problem was overcome in this work by the use of hot filament assisted gas carburizing. Due to chemical reactions occurring near the hot filament, the gas mixture, initially consisting of methane and molecular hydrogen, was enriched by atomic hydrogen [2], drastically decreasing the content of free oxygen in the carburizing atmosphere.The second part of this article concerns the theoretical analysis of reasons that lead to the development of the experimentally observed morphology of the diffusion zone. In particular, the influence of the growth stresses on the morphology of an interphase boundary is investigated."

Jan 1, 1996

By M Kolbe

Co-Cu exhibits a metastable miscibility gap in the region of the undercooled melt. Specimens have been undercooled and solidified containerlessly into the metastable miscibility gap in an electromagnetic levitation facility (EML) and in drop tube (DT) experiments. Due to the high undercooling the velocity of the solidification front is very high and the microstructure is frozen in instantaneously. The microstructure of samples processed in the EML is influenced by the electromagnetic stirring due to the induction of electrical currents into the melt. A variety of microstructures has been observed. After undercooling below the binodal the liquid melt separates into the Co-rich L1-phase and the Cu-rich L2-phase. Two basic morphologies of the L1-phase can be observed, they can be attributed to the transition in dendrite growth from diffusionally and thermally controlled to only thermally controlled growth. Transient microstructures are observed after solidification in the vicinity of the binodal. Drop tube experiments, which lead to a rapid solidification of a distribution of droplets under reduced gravity conditions, in contrary allow for the observation of the early stages of demixing: the microstructure shows a homogeneous distribution of spherical particles of the minority phase in the droplets. The cooling rate of the droplets and its dependence on the droplet radius has been calculated. The solidification velocity as a function of undercooling has been measured in the EML for the composition Co-lB.Bat%Cu. The data are analysed in the framework of the LKTlBCT model with a velocity-dependent distribution coefficient as well as within a model of Galenko and Danilov using a kinetic growth coefficient of u=0.22 m/Ks.

Jan 1, 2002

By J. R. Odekirk

The nature of mineral distributions and locking characteristics in mill products are important factors in understanding mill performance. Such data are obtained by microscopic point counting methods. Reduction 'of point-count data from volume to weight percentages, and reduction of data for each size fraction back to a head sample requires lengthy hand calculations. The use of computer processing for such data reduction results in obtaining information on a realistic time basis. An example of computer processed point-count data is presented.

Jan 1, 1981

By P. M. Tyroler

Inco operates a hydrometallurgical plant to treat the residue from the pressure carbonylation process. The main constituent in the residue is cop¬per. The residue is leached under pressure in an acid sulphate solution in two stages and the copper is recovered via electrowinning. The electrowinning tankhouse is fully integrated into the overall plant flowsheet as spent elect¬rolyte is required in upstream leaching steps. In recent years, the amount of residue had increased and copper removal capacity became the rate limiting factor for the entire plant. Consequently, a major program was undertaken to upgrade the tankhouse with regards to capacity, efficiency, cathode quality, working environment and structual integrity and appearance. This paper will describe current facilities and operation, and detail progress in our up¬grading efforts.

Jan 1, 1987

By Run-bo Wang, Zhe Wang, Fan-yi Meng, Jian-Liang Zhang

The influence of semicharcoal substitution for coke breeze on sintering performance was investigated by pot-grate sintering test. At a fixed fuel ratio, sinter productivity and strength decreased with the substitution increasing from 0 to 100% due to better combustibility. To enhance the utilization efficiency of 100% semicharcoal, sintering parameters (moisture and suction pressure) was adjusted. With the moisture increasing, sinter performance of 100% semicharcoal increased because of the suppression of semicharcoal incomplete combustion. As the moisture further increasing to 9.0%, sinter quality gave rise to a decrease trend. The results also showed that the increase of suction pressure was benefit for the increase of heat transfer rate, leading to the improvement of heat utilization energy. Measures to enhance magnetite oxidation during sintering are discussed based on current understanding of the fundamentals that control the sintering process.

Jan 1, 2015

By R. T. Seaman

Pressure oxidative treatment of whole ores and/or mineral concentrates is used to leach or liberate metals of value for downstream recovery. Silver, when present, is often lost in processing, precipitating as a cyanide-insoluble jarosite in the residue. Depending on pressure oxidation conditions, the degree of silver loss to jarosite can vary dramatically. Batch bench-scale testwork is often performed to define that loss, and then assess the implications in continuous operations. This paper focusses specifically on the impact of CESL pressure oxidation conditions on silver recovery, and discusses limitations of batch bench-scale testing as well as means of overcoming these limitations to better predict silver recovery in the scale up from bench-scale to continuous operations. Since silver is only partially soluble in both sulphate and chloride media, it will gradually leach and deport to a jarosite as oxidation progresses. When a silver-insoluble anion, for example iodide, is dosed prior to oxidation, there is a marked improvement in silver recovery from batchgenerated residue; however, that benefit is not consistently seen in continuous operations. The difference has been attributed to the dynamic solution conditions in the batch test, specifically the first few moments of oxidation. Using these principles, a predictive correlation has been established between initial leach concentrations of iron and acid and ultimate silver recovery with iodide addition.

By Pedro A. Netto, Giulio R. Altoé, Sergio N. Monteiro, Ygor M. Moraes, Frederico M. Margem, Gabriel O. Glória

Since environmental issues are becoming more and more important Worldwide. Nowadays, Natural fibers are been used to substitute the synthetic ones. Although PALF fiber is an important natural fiber and its mechanical Properties surpass in various aspects some other lignocelluloses fibers, such few studies have been conducted with the fiber obtained from leaf of PALF plant. In order to better evaluate the mechanical properties and possible applications, this paper aims to improve the elastic modulus of the PALF fiber by Weibull statistics, by evaluating their mechanicals properties and possible applications. The fibers were divided in diameter intervals and the tensile strength and elasticity modulus were measured in each range. The fractured surface was examined using scanning electron microscopy. The results, interpreted by the Weibull statistical method, showed a correlation between the fiber elastic modulus and its diameter.

Jan 1, 2015

By Hongbo Zhao, Jun Wang, Wenqing Qin, Guanzhou Qiu, Xueduan Liu

Bio-hydrometallurgy technology was applied for the extraction of copper from the raw ores of Chambishi Mine in Zambia. A copper extraction of 93.29% was obtained for small scale column bioleaching within 63 days, while a copper extraction of 89.05% was achieved for large scale column bioleaching in 90 days, thus confirming the amenability of the raw ores for effective extraction via bioleaching. The bacteria were cultured in a 6-stage enlarge cultivation. The bacterial cultures with cell concentration of more than 1×108 cells/mL were added into a spray pond of sulfuric acid to be applied in the dump leaching, and a copper extraction of about 50% was achieved within 2 months. The production report revealed that the copper extraction increased by approximate 20%, and the acid consumption was reduced to around 35% as a consequence of adding the bacteria. The industrial demonstration of the bio-hydrometallurgy technique is now well established in Zambia, and further applications of bio-hydrometallurgy in both Zambia and Congo are currently in progress.

Jan 1, 2015

By Zhang Duomo

A novel homogenous precipitation method, including microwave heating, solution conductivity controlling and freeze drying, was developed for the preparation of US nanoparticles. The effects of the precipitation conditions on the structure and morphology of CdS particles were discussed individually. It was found that under the experimental conditions the particle sizes were controllable in the range of 14nm to 100nm. Blend-type CdS was obtained from nitrate or sulphate solution and the more stable wurtzite-type US was obtained from chloride solution, which was ascribed to the coordination of C1 and Cd2+ altering the supersaturation of the solution as well as the different growth units and their connecting patterns, In the precipitation process the surface of US nanoparticles were surface modified with CH3CHSCOOH. The results demonstrate that the bifunctional thiols of thioglycolic acid modified the surface through Cd-S coordination bonding and the induced counter ion AOT-SO3 as the balance charge further increased the stability and dispersity of US nanoparticles. This surface-modified US nanoparticles had been used to prepare nonlinear optics and self-assemble catalysts.

Jan 1, 2003

By Raymond E. Healy

Mercurian e1ectrum (Au-Ag-Hg alloy) is the principal Au-bearing phase in the massive sulphide ores at Trout Lake, Manitoba. The average composition of this phase (in wt %) is 49.2 % Ag. 38.7 % Au and 11.0 % Hg, with ranges of 17.34 to 76.47 % Ag, 1.62 to 79.86 % Au and 1.29 to 30.87 % Hg. Compositional variation reflects solid solution in the a-phase of the Ag-Au-Hg system. Backscatter electron imagery reveals systematic zoning and suggests a general crystallization sequence from metamorphic pore fluids of progressively Ag-rich compositions. Investigation of the occurrence of gold in mill products demonstrates that mercurian electrum accounts for over 90 % of the Au in Trout Lake ore. I Invisible" gold in pyrite (x = 0.72 ppm Au) and arsenopyrite (x 30.2 ppm Au) is confirmed by SIMS analyses, and accounts for 7-10 % of the Au in the ore, and 35 % of the Au lost to the tailings. The remaining 65 % of the Au lost to the tailings consists principally of mercurian electrum locked with pyrite. No significant losses of mercurian electrum in the size range amenable to flotation and/or regrinding is indicated.

Jan 1, 1989

Numerical simulation of the fluid flow and heat transfer has been carried out for a waste-heat boiler in an Outokumpu type copper flash smelter. In this boiler, SO2-containing off-gas flows into the waste-heat boiler radiation section at about 1350°C. A fraction of cooler off-gas from the electrostatic precipitator at about 200°C was recirculated into the radiation section, and a small amount of ambient air was leaked into the boiler from the bottom. The computational results show that the flow is strongly recirculating and distinctly three dimensional in most of the boiler, particularly in the radiation section. The hot off-gas cooled down rapidly after entering the radiation section due to radiation. The predicted flow pattern and temperature distribution were in a good agreement with laboratory models and industrial measurements.

Jan 1, 1995

By Bing Gao, Zhe Wang, Xiangdong Xing, Xueqi Zhang, Shan Ren, Jianliang Zhang

"In sintering, the flame front speed (bed permeability) and sinter qualities are greatly depended on the feed size, especially coke breeze and limestone particle size. It is well known that coke breeze provides sinter bed with heat to meet the demand of partial fusion and diffusion bonding while limestone reacts with iron ore to generate bonding phase in the sintering process. Accordingly, it is necessary to find the optimum combination of different particle size of coke breeze and limestone to yield sinter associated with better qualities. In this study, sinter was produced in the sinter pot with varying coke breeze and limestone particle size together in sintering of a coarse hematite iron ore. The sintering productivity was measured and all of the result sinters were examined by microstructure analysis and reduction degradation test (RDI test). For the sintering of a coarse hematite iron ore, it was found that the optimum mean particle size combination of coke breeze and limestone was 1. 71mm and 1.55mm in the sinter mix. On such a circumstance, sintering productivity was higher and the properties of sinter were better.IntroductionNowadays, as the main iron bearing burden material of modem blast furnaces, sinter has a great influence on the blast furnace operation. Sintering is a greatly complex process involving various chemical reactions to form kinds of mineral phases [1, 2]. In the sintering process, coke breeze is used for fuel and it generates heat to raise the green bed temperature. Limestone serves as flux and it reacts with iron ore to produce various mineral phases. On one hand, during the sintering process, the particle size of coke breeze can have an effect on temperature, atmosphere, the flame front speed and all of them act on the microstructure and mineral constitutions of sinter [3, 4]."

Jan 1, 2013

By Akira Yazawa

Experimental results for the distribution ratios of various elements between the slag, matte and/or copper in the silica-saturated copper smelting system were summarized. The experiments were carried out under an oxidative smelting condition with S02 gas flow, and also a reductive smelting condition equilibrating with metallic copper or iron. To evaluate the results thermodynamically, the availability of one atom cation base expression for the constituent compounds is emphasized from both of theoretical and practical standpoints. Both of oxidic and sulfidic dissolutions in slag are postulated for some elements such as copper, nickel and lead., and the experimental results are reasonably explained thermo-dynamically. The results for the mutual solubility between matte and ferrite slag and the distribution of minor elements between liquid copper and ferrite slag are also discussed.

Jan 1, 1983

By Ivo André

Sorption of copper ions from aqueous solutions by dried biomass of the aquatic plant Potamogeton luscens was studied at laboratory scale. The aquatic plant was collected in water resources in Brazil, washed, dried at 60°C and ground in a bladed mixer. Sorption experiments were conducted in agitated flasks and in a packed bed column. Maximum copper removal was obtained between pH 5.0 and 6.6 when copper was present in the ionic form Cu'. Sorption followed the Langmuir isotherm with saturation attained at 35 mg/g. Free energy of sorption was found, to be of the order of -25 kJ/mol. Sorption kinetics data were better described by a second order reaction and rate constants were calculated in 0.030 1/(min.mg) for - 4.0 mm particles and 0.081 1/(min.mg) for - 0.59 mm particles. Removal of metal ions in a packed bed column showed that Potamogeton luscens biomass can be used in several sorption/dessorption cycles. After sorbent saturation, copper ions can be recovered from the loaded biomass by elution-with H2SO4, solution. Main mechanism responsible for heavy metal uptake was found to be ion exchange. Results are discussed in terms of the surface properties of the biomaterial, solution chemistry of copper ions and thermodynamics parameters.

Jan 1, 1995

By Qing-Yun Huang, Xiao-Yi Zeng, Bing Xie, Hong-Yi Li, Jia-Rong Yan

"In order to utilize vanadium resource in vanadium-titanium magnetite ore efficiently, vanadium distribution ratio between hot metal and slag should be improved during BF process, meanwhile the precipitating of Ti(C,N) in slag must be minimized. Effects of temperature, Ti02 content in the slag and basicity on vanadium distribution between slag and hot metal were investigated by experiment and thermodynamic calculation. The results indicated that high temperature, low Ti02 content and high binary basicity of slag were beneficial to increase the vanadium distribution ratio. The effects of temperature and Ti02 content in slag on vanadium distribution were stronger than that of slag basicity.IntroductionVanadium is an important element that is widely used in industrial fields. Most of vanadium resource is hosted in vanadium bearing titanomagnetite [l]. Vanadium bearing titanomagnetite is thus one of the domainate raw materials to produce the vanadium products. In other words, the comprehensive utilization of vanadium bearing titanomagnetite is beneficial for vanadium resource utilization. Vanadium bearing titanomagnetite sources are abundant in Pan Xi of China [4]."

Jan 1, 2013

By Wang Yun-yan

In order to examine the adaptability and the kinetics of leaching different gold ores in alkaline thiourea system, six kinds of gold concentrate and/or calcine with different physical and chemical properties were chosen as objects. The leaching behaviors in alkaline thiourea system with high stability, acidic thiourea system and alkaline cyanide system were compared. Changes of phase, surface appearance, particle distribution and specific surface area of six kinds of gold ores before and after leaching were studied in virtue of modern analytic techniques, e.g., XRD, SEM, and so on. The results indicate that alkaline thiourea solution can be used to leach gold ore, for oxidized gold concentrate removed arsenic by microbe pretreatment(4#) the leaching rate of gold is up to 82.68%, such conclusion overthrows the parlance reported that pH value must be less than 1.78, or gold can not dissolve in thiourea solution. Chemical components and phase are related to gold leaching rate, different gold ores are fit for different leaching system, and alkaline thiourea solution is suitable for the pretreated oxidized gold ores with low content of sulfur and in which the main phase was SiO2, phase almost does not change after leaching basically. Generally speaking, when leaching in alkaline thiourea solution, surfaces of gold ores with glaze change greatly to ones with coarseness, distinct trace and holes of corrosion. Particle size decrease and specific surface area increase of gold ores after leaching in alkaline thiourea solution with high stability except gold concentrate of Zhongyuan gold smelter(5#).

Jan 1, 2006

By James R. Craig

The General Image Processing System (GIPSY) is being employed for the quantitative textural analysis of complex sulfide ores from the Southern and Central Appalachians and for the determination of liberation characteristics of the mineral constituents during grinding. Optical images from a microscope-mounted TV camera or from 35mm film are converted into digital images which are subsequently analyzed by GIPSY, a transportable image processing software package. Properties measured by GIPSY include spatial distribution of mineral constituents, grain sizes, grain shapes, grain orientation and mineral co-occurrences.

Jan 1, 1982