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By Dongping Duan, Hongliang Han, Li Zhong, Siming Chen, E Zhou

In this study, physical, chemical and microscopic characteristics of Celestine were investigated firstly. Based on which, the thermodynamic analysis of Celestine reduction was discussed. And the experiments of Celestine carbon-containing pellets used in rotary hearth furnace process were studied. The results showed that it is feasible to deal with Celestine by rotary hearth furnace direct reduction process. When the temperature is 1200°C, C/O ratio is 0.8 and holding times is 20min, the conversion rate of SrSO4 in Celestine is above 95%, the utilization rate of Celestine is nearly 100%. This study can provide theoretical and technical basis on economical and rational use of Celestine.

Jan 1, 2016

By M. Oliazadeh

Spodumene [LiAl(Si2O6)] is the most common and desirable economic lithium-bearing mineral due to its high lithium content. In Canada, there are several spodumene deposits at the development stage that have the potential to help narrow the forecast lithium supply gap stemming from the widespread acceptance and increasing use of electric vehicles. Spodumene processing can be conducted using Dense Media Separation (DMS), flotation or combination of both. If spodumene liberation is sufficient at coarse particle sizes, DMS can be used for primary lithium concentrate production and silicate gangue minerals rejection. If liberation is not sufficient, flotation is then the main processing route for spodumene concentration. Even in cases where DMS is a viable beneficiation option, flotation may still be required to process the DMS middlings and/or the undersize fraction which is outside the particle size range for DMS. Considering flotation as a technique for spodumene beneficiation, there are several alternatives including the use of mechanical flotation cells, column flotation cells, coarse particle flotation cells, and/or Staged Flotation Reactors (SFR), either alone or in combination. Ore sorting can be incorporated at the start of the spodumene flowsheet to remove gangue minerals, particularly amphibole and pyroxene in the early stages. The main objective of flowsheet development for hard rock lithium deposits is to evaluate the ability of these options to produce a spodumene concentrate with a concentrate grade above 6% Li2O, lithium recovery of above 80%, and with the minimum operating and capital cost. This paper aims to describe the various processing options available for the beneficiation of spodumene from hard rock deposits and compare the associated operating and capital costs for each.

By Richard D. Hagni

Quantitative techniques have become increasingly important in recent years in the study of ore minerals. Precise measurement of indentation hardness and reflectance is the most important quantitative ore microscopic technique for mineral identification. Reflectance measurements of various wave lengths under monochromatic light provide the data necessary for the preparation of spectral reflectance curves and for the quantitative determination of an ore mineral's color. The procedures for the measurement of indentation hardness, reflectance, and color coordinates have recently been standardized and 204 items of quantitative data for ore minerals are now available in the first issue of the quantitative data file of the International Mineralogical Association's Commission on Ore Microscopy. A number of systems utilizing these quantitative data for systematic ore mineral identification have been published and others are in preparation. Rotation properties, although not included on the data cards, are useful in the identification of certain groups of minerals. Other aspects of quantitative ore microscopic techniques include the utilization of automatic image analysis for mineral percentage determinations and the use o~ various microbeam instruments for elemental analyses. These techniques provide a greatly improved basis for mineral identification in mineralogical and beneficiation studies.

Jan 1, 1981

By T. A. George, David J. Sellmyer

"The concept of achieving a useful high-energy-product magnet through appropriate nanostructuring of known hard and soft phases has been tantalizing researchers since the idea was first proposed. The fabrication of exchange-coupled nanocomposite magnets faces several challenges including aligning the easy anisotropy axes of the hard-phase grains. Here we investigate experimentally two-phase nanostructures of hard Lio-ordered FePt and soft iron-rich/cc Fe(Pt). The Fe-Pt thin films were produced by epitaxial cosputtering onto MgO (001) single-crystal substrates which lead to strong (001) texturing. The measured hysteresis loops indicate nearly ideal exchange coupling. Excellent magnetic properties are obtained, with largest values of coercivity (51 kOe), saturation magnetization (1287 emu/ cm3, J, = 16.2 kG), and nominal maximum energy product (58 MGOe).1. IntroductionA key figure of merit for permanent magnets is the maximum energy product (BH)rrw.x. The achievable maximum energy product is determined by a magnet's saturation magnetization M, and its magnetic anisotropy. For example, it is well known that (BH)rrw.x :S 4n2M,2• In the past, record energy products have been the result of discovering new compounds with high values of magnetization and anisotropy. However, finding new compounds with better magnetic properties than the current record-holding magnet Nd2Fe14B has proven to be difficult. A different approach is to exploit the exchange coupling mechanism between known hard and soft magnetic phases to enhance the maximum energy product [1-5]. In such a composite system, high coercivity is achieved due to the anisotropy of the hard phase as well as a nanostructure which prohibits large-scale domain wall reversal mechanisms. Magnetization is enhanced by the soft phase and loop squareness results from texturing of the hard phase easy-axis as well as complete exchange coupling between the coexisting hard and soft grains."

Jan 1, 2012

By Rina Kim

There are many factors which affect the gold cyanidation mechanism— mineral composition, free cyanide and dissolved oxygen (DO) concentrations, heavy metal additions, etc. This study combines electrochemistry and surface analysis methods to examine the effectiveness of the above factors on gold cyanidation process. Three gold ore samples were used in this study. Sample 1 was a pyrite concentrate, contained mercury and silver. Sample 2 also contained sulfide minerals, including galena. Sample 3 contained pyrite with sphalerite and galena. In the case of samples 1 and 2, the presence of heavy metals enhanced gold cyanidation kinetics, though the addition of higher DO was not effective on improving the kinetics. Sample 3 showed an opposite behavior: the kinetics was not enhanced by galena, because of its relatively small amount, however, the use of higher DO made improvement in the gold leaching kinetics, likely caused by iron species generated by pyrite oxidation.

By H. V. R. von Rhaden

Systematic quantitative X-ray diffraction analyses performed on diamond-drill cores originating from the Aandenk formation at the Loraine Gold Mine, located in the Welkom goldfield, Orange Free State, South Africa, have revealed the presence of a number of phyllosilicate mineral assemblages which have not hitherto been reported from this region. Rectorite, a regularly interstratified 1:1 mica-montmorillonite "swelling clay", is found to occur together with paragonite, muscovite, pyrophyllite, kaolinite, and chlorite in highly-altered friable rocks. The presence of rectorite in mill feeds may have potentially serious implications with respect to gold recovery. Quantitative X-ray diffraction analysis for phyllosilicates can be used as an aid to correlation, and also to guide the widths of stopes in underground mining. Rectorite has a unique mode of origin, which is discussed.

Jan 1, 1991

By Qian Li, Li-chen Hou, Yong-bin Yang, Tao Jiang, Jian-jun Hu, Bing Xu

Extraction of gold from refractory gold concentrates usually requires an oxidation step to remove arsenides、sulphides and carbonaceous matter. In this investigation, the gold concentrates were two-stage roasted under different atmospheres and temperatures. Results indicated that at the first stage, under neutral atmosphere, the removal rate of arsenic increases as the temperature rises. Under the oxidizing atmosphere, with the increase of temperature, arsenic content in the residued calcine increases, in addition, the volatilization of arsenic is also affected by the oxidation of carbon that generated CO, which is advantageous to the decomposition of arsenate decomposition. At the second stage of roasting, it is the higher temperature and stronger oxidizing atmosphere, the faster sulfur and carbon oxidated rate is, but at the same time, the calcine appears the phenomenon of consolidation because of the phase of silicate compounds generate.

Jan 1, 2015

By Carla Lupi

Zinc electrowinning from sulfate solutions is the traditional industrial method to produce SHG zinc. Over the past few years several efforts have been done to improve process efficiency in order to reach high productivity with low energy requirement. The latter aim can be pursued both by means of a hard purification of the electrolyte and reducing the anodic voltage. This work is a comparative study of the results obtained in several previous researches on zinc electrowinning from both sulfate and chloride solutions. Zinc electrowinning tests on industrial sulfate solution have been carried out by using Pb alloy anodes and by adding organic depolarizers such as ethanol, acetic acid or ethylene glycol. Experiments on chloride solutions, obtained by purification of zinc exhausted electrolyte, have been performed by using DSA anodes and by testing the effect of additives such as TEACI and TBAC\. Comparing the best results obtained with the two methods it can be highlighted that a high quality zinc is electrowon in both cases with comparable energy requirements.

Jan 1, 2000

By B. Nowak

For sources with an iron-to-vanadium ratio of far above 1, it is proposed to leach in acid and to oxidize under autoclave conditions. During this oxidation process, it is experimentally shown that divalent iron contained in this solution will be oxidized to trivalent iron, whereas free acid contained will be consumed by this reaction. In case no acid is present or already fully consumed, a solid consisting of ferric compounds and an iron-vanadium-co-precipitate will form that can be filtered from the solution. If choosing the right reaction conditions, this filter cake has an iron-to-vanadium ratio of close to 1, whereas the liquid remainder is almost vanadium free. This precipitate, identified as FeVO4, 1.1 H2O, can be processed by conventional technologies such as caustic leaching, or probably salt roasting or reduction with aluminum, yielding common marketable products.

By I. J. Moon

The reduction behavior of hematite by H2 and H2-CO gas mixtures was investigated to elucidate the reduction mechanism at 800-950 °C. The hematite compacts were made by Cold Isostatic Pressing to produce compacts of uniform shape and size. The compacts were sintered at 1000° C for 30min, and showed a contraction of 29%. Mercury pressure porosimeter was used for measuring the total porosity, pore size distribution and pore surface area of the compacts. Reduction was measured by means of weight-loss technique using Cahn Balance (Model : TG-171, capacity log, accuracy f 10pg). Microscopic examination and X-ray analysis were used to correlate the structure of reduced compacts with the mechanisms of reduction. Neither chemical reaction control nor diffusion control is adequate in describing the complete course of reduction of the hematite compact. The reduction of hematite compacts was initially controlled by the chemical reaction at oxidelmetal interface. The reaction goes through a transition phase .where it is undergoing a mixed control, followed by the diffusion control towards the end of the reduction. The values of apparent activation energies for chemical reaction control were 3.48-8.43 kcal/mol depending on the gas compositions.

Jan 1, 1997

By Ajit Kumar Jaiswal

"Electric Arc Furnace (EAF) being a power-intensive equipment, EAF based industries are highly dependent on scarce electric energy. This is the reason Government of India is highly concerned about this and laid emphasis on the conservation of electric energy.This paper highlights factors contributing to reduction in specific electric energy consumption in EAF and suggests measures not only for power saving, but also for productivity improvement. To name a few, these are proper sealing of furnace, introduction of oxy-fuel burners, foamy slag practice, increased usage of hot metal/DRI, post-combustion of CO gas for preheating of scrap, improved selection & design criteria of electrics, power demand management, and process automation. Few cases also have been cited, where the above measures have helped in reaping significant benefits.IntroductionFor a long time, Government of India had focused on increase in energy supply, in particular, through electricity generation. Now the emphasis of Government of India has shifted from electricity generation to its conservation for following two reasons:??Power plants have become very cost-intensive??By saving energy, more of it can be delivered at lower cost to the consumersPower generating units, transmission & distribution agencies as well as consumers all have roles to play in the area of energy conservation. By energy conservation, we mean curtailing energy requirement by reducing energy wastages and taking up measures to improve energy efficiency of electric equipment/appliances. In almost all cases, this would be economically beneficial.India’s cost-effective energy conservation potential has been estimated by the Planning Commission at 23 per cent of total commercial energy generated ?1?. A national movement for energy conservation can significantly reduce the need for fresh investment in energy supply systems in coming years. It is imperative that we make all-out effort to realize this potential. Whether a household or a factory, a small shop or a large commercial building, a farmer or an office worker, every user can and must make this effort for his own benefit and for the nation’s benefit as well."

Jan 1, 2009

By David Melgaard

A significant emerging recycling, waste minimization problem stems from legacy waste from the nuclear weapons program and from production of power using nuclear fuel. Premium quality metals used in nuclear plants become contaminated, making them unsuitable for reuse. Consequently, decontamination studies were conducted to evaluate the decontamination capacity and partitioning effeetiveness of Electroslag Remelting (ESR). Eight laboratory melts were conducted to evaluate the efficacy of using ESR to transport radionuclides from the liquid metal phase to the liquid flux or slag phase. To determine the decontamination effectiveness, several surrogate compounds for uranium, plutonium and other fission products were added to the melts. During the melts, the melting rate was varied, typical slag additives were used, and two different slag compositions were evaluated. The resultant post-test ingots and slag were then analyzed to determine the partitioning of the surrogates. ESR generally proved very effective in removing contaminates from the metal with a few noted exceptions. -

Jan 1, 2003

By Omid Marzoughi

Chromium has a wide range of applications, including as an alloy addition in various steels and also as a corrosion resistance coating. Carbothermal reduction of chromite ore (FeCr2O4) in a submerged arc furnace is an important industrial process for extracting chromium, but the energy consumption is excessive. It is suggested that one area for future research is the low temperature carbothermic solid state reduction of chromite to produce an intermediate product, which can subsequently be upgraded to ferrochromium. In this regard, a thermodynamic model has been developed to investigate this process and the effects of temperature, carbon additions and ore composition on the recovery of chromium and the grade of the ferrochromium, have been studied. Further development of the model may allow it to be applied to the simulation of other processes for the recovery of chromium from chromite ores.

By Andreas Siegmund

Cast or rolled lead anodes employed in zinc electrowinning typically contain between 0.5?1.0% silver to decrease the overall corrosion rate. 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 internal corrosion in localized areas. In rolled anodes the presence of internal porosity is significantly reduced, thus resulting in extended service life. The obtained grain structure of cast or rolled Pb-Ag anodes, however, requires a relatively long period of time to form a stable protective PbO2/MnO2 layer that can evolve oxygen without excessive lead contamination of the cathode. Therefore, these anodes are often mechanically, chemically or electrochemically conditioned prior to being placed in the electrowinning process. RSR Technologies has developed an improved anode for zinc electrowinning. The anode consists of a rolled Pb-Ag-Ca-alloy with controlled surface grain structure. The preferred calcium and silver content of the alloy is 0.05?0.08 % and 0.3?0.4%, respectively. Since May 2001, industrial-scale tests have been carried out at two zinc refineries in North America in industrial electrowinning cells. The controlled grain structure of these anodes allows forming an adherent protective oxide coating within a short period of several days when placed in an electrowinning cell without the necessity of being preconditioned. Anode sludge growth is evenly distributed. The anodes stay dimensionally stable and no short-circuits have been observed. Consequently, low corrosion rates and improved current efficiencies have been achieved.

Jan 1, 2003

By Shengfan Zhou, XUEWEN WANG, Bianfang Chen, Mingyu Wang

Vanadium was leached from roasted stone coal by NaOH solution, and the effect of leaching temperature, leaching time, addition of NaOH, liquid to solid ratio, the grinding fineness of stone coal, and stirring speed on the vanadium leaching rate was studied. The kinetics analysis for the process is presented by the shrinking core model. The results show that the vanadium leaching ratio of roasted stone coal can be beyond 75% at the 6% NaOH addition, leaching temperature of 95°C, leaching time of 7h, liquid to solid ratio of 1.2mL/g, and grinding fineness of 0.111mm. The leaching process is controlled by interfacial reaction kinetics and the apparent activation energy was 59.36kJ/mol.

Jan 1, 2016

By R. G. Reddy

Nickel solubilities in spent pickling solutions (i.e. HF-HNO3-H2O solutions ) were measured as a function of HF and HNO3 acid concentrations. The chemical analysis of the industrial pickling solutions and sludges were made. The stable phases observed in the sludges are FeF3?3H2O, and ( FeCr ) F3?3H2O. Pure Ni, and stainless steel type 316 were used in this study. The results showed that the solubility of Ni increased with increase in concentrations of HF in pickling solution at a fixed concentration of HNO3: An excellent agreement between the experimental solubility data and the theoretical data was obtained. X-ray diffraction analysis showed that the solid solubility product formed is mainly NiF2?4H2O compound.

Jan 1, 1992

By Ali Hasham

Reduction rates of FeO in CaO-SiO2-Al2O3 slags by Fe-C melts have been investigated experimentally at 1723 K. The rates were estimated using experimentally determined CO(g) evolution rates. Flash X-ray images were employed to visualize the behavior of the melt-slag interface during the reactions. The influence of melt interface was examined by conducting two types of experiments - (i) dropping one (or several) Fe-C droplet(s) weighing 2 g into the molten slag bath, and (ii) dropping a small amount (10-30 g) of slag onto a Fe-C melt weighing 400 g. The rates from both types of experiments were compared and analyzed to determine the rate limiting steps. It was established that neither the carbon transport in the Fe-C melt, nor the transport of gas species in the gas film adjacent to Fe-C melt was responsible in limiting the reaction rate. It is possible that the slag phase mass transport may be controlling the initial reduction rate in the droplet experiments. However, a, different mechanism was responsible in limiting the reduction reaction when the overall %C in the droplets fell to about 2-3.

Jan 1, 1992

By Wu Liu

A modified falling ball technique for measuring the viscosity of liquids is described. It consists of recording the weight vs. time of a crucible holding the liquid of unknown viscosity, as a solid ball, or liquid drop, is let to fall through the liquid. This method does not require measurements at constant terminal velocity, as the conventional falling ball technique. Also, measurements do not depend on visual observation, which is not possible in opaque liquids or containers. The effect of process parameters on the utility of this method and its potential application to liquid systems of metallurgical interest were analyzed theoretically. The paper also com- pares the gravimetric method to the conventional falling ball technique for measuring viscosity.

Jan 1, 1992

By Joseph Hamuyuni, Pekka Taskinen

We present experimental results for the liquidus in the system Cu2O - CaO -Al2O3 at 1250 oC. In this study, we quantified the liquidus by the equilibration/quench/analysis technique, with Cu2O, Al2O3, and CaO as primary materials exclusively. Experiments were conducted in air at an at oxygen pressure (p) = 21.3 kPa). Equilibrated specimens were quenched in brine solution of 10 wt% NaCl. We then quantified the liquid chemical compositions by means of Energy-Dispersive X-Ray Spectroscopy (EDS) and Electron probe micro-analyzer (EPMA). This study reveals inconsistences in liquidus surface of the present ternary diagram of the system here in mentioned. Differences of up to 10 wt % compositions of the species have been observed.

Jan 1, 2015

By Yuanbo Zhang, Yongbin Yang, Guanghui Li, Zhengwei Yu, Yufeng Guo, Tao Jiang, Xiaohui Fan, Youming Hu

"Composite agglomeration process (CAP), as an innovative method for preparing blast furnace burden, was developed and has been put into operation in China. CAP is different from traditional agglomeration processes of iron-bearing materials involving sintering and pelletizing. Compared to the traditional agglomeration processes, CAP is characterized by several strengths such as permission of diverse iron-bearing materials in production, obvious improvement of permeability in the feed bed, decreasing the fuel consumption and remarkably increasing the productivity of sintering machine. Furthermore, the use of the composite agglomerates prepared with CAP is capable of obviating the negative effects caused by the differences in quality of sinter and pellets on the operation of blast furnaces. This paper mainly presents an overview of the principle and applications of CAP.Development Background and Principle of CAPhe traditional agglomeration processes including sintering and pelletizing have been the two predominant methods for preparing ironmaking burden from iron-bearing materials. Sintering is a way for agglomeration by heating the coarser fine ores (general granularity 0~10mm). The mechanical strength of irregular porous sinter is obtained by the solidification of molten phase at high temperature process. It has been shown that the production of high basicity sinter (R=1.8~2.2) is characterized by low energy consumption and high efficiency compared to low basicity sintering. Meantime, the finished high basicity sinter is characterized by good mechanical strength and metallurgical performance. Pelletizing is another way for agglomeration by firing wet green pellets, which are balled from the fine grained iron ores or concentrates. Based on the differences of chemical compositions, the finished pellets can be divided into acidic oxidized pellets, fluxed pellets, magnesium-bearing pellets, and so on. The acidic oxidized pellets are the dominant products of modern pelletizing."

Jan 1, 2012