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By Jiang Diao, Yong Qiao, Xuan Liu, Tao Zhang, Bing Xie

Adding CaO into the vanadium extraction converter is an effective way to decrease the dephosphorization burden in subsequent steelmaking process. The crystallisation process of spinel is one of the most decisive factors in the subsequent extraction. The theoretical calculation results show that the temperature of the peak total crystallization rate will decrease 5K with basicity increasing 0.1. The relation between cooling conditions and grain size of spinels is also discussed. It is found that low cooling rate and high basicity benefit spinel crystal growth. And the non-isothermal crystallization kinetics results indicated that the restriction factors of spinel growth is that solid crystals accept new components from liquid-solid interfacial. While the sample was cooled down to 1250 (1523K) at cooling rate of 5K/min, the crystal growth is consistent with Ostwald coarsening grew up law, and controlled by diffusion of particle.

Jan 1, 2016

By C. F. Feng, L. Froyen

"In-situ processes have emerged as new and promising techniques for metal matrix composite fabrication. They offer significant technical and economic advantages over conventional processing. One of the in-situ processing routes that have been used is reactive free sintering of a mixture of powder reactants. However, materials synthesised via this route are always porous because of density differences between reactants and products. An example are the porous Al/(TiB2+Ah03) MMCs obtained by heating powder mixtures of Al+ Ti02+B with Ti02 and B in stoichiometric ratios for forming TiB2• In this study, porous Al/(TiB2+Ah03) composites were further processed by hot-pressing at temperatures above 600°C. This processing cycle was designed so that the composites could be densified. Furthermore, the reaction kinetics of the in-situ processing are studied by means of DSC analysis measured at different heating rates. The activation energies of the three intermediate steps that are involved in the reactive processing for preparing AV(TiB2+Alz03) MMCs are determined to be 923 kJ/mole, 241 kJ/mole and 235 kJ/mole respectively.XRD proved that the hot-pressed products consist of Al, TiB2 and Al203- Properties of the products are assessed by microstructural characterisation (LOM, SEM and EDS), microhardness, Young's modulus and bending tests. The results show that good microstructures, elastic properties and strengths, as well as acceptable ductilities were achieved. For the composition 79.74wt% Al-15.95wt% Ti0z-4.31wt% B, after the reactive free-sintering and hot-pressing cycles, Young's modulus is 105 GPa, bending strength is 509 MPa and maximum strain is 5.0%; for composition 88.73wt% Al-8.87wt% Ti0z-2.40wt% B, they are 89 GPa, 311 MPa and 8.2% respectively. It can be seen that the properties of products can be tailored by adjusting the relative amounts of reactants in green samples. Furthermore, for comparison reasons, Al and a binary system Al-Ti02 were identically processed as the ternary systems. Their microstructures and properties were studied."

Jan 1, 1998

By Zhenbo Zhao

The processes and equipment for INLRFH (Isothermal Normalizing by Utilizing the Residual Forged Heat) of alloy carburizing steel products are presented. It is shown that four key parameters: namely (I) cooling rate before isothermal normalizing, (IT) the lowest cooling temperature before isothermal normalizing, (111) isothermal normalizing temperature and (IV) isothermal normalizing time, should be controlled. The prediction and calculation of these parameters can be achieved on the basis of components treated and the technical requirements of the steel parts by an on-line expert system. The cost-reductions due to the energy savings resulting from implementing this system for automotive parts heat-treatment are most promising.

Jan 1, 1999

By Mathilde Guilpain

A wide variety of plants are able to extract nickel (Ni) from soils and accumulate this metal in their foliage. Hydrometallurgical processes have been developed to recover Ni in the form of metal or salts, starting from the plant A. murale. They include: (1) a combustion step, to obtain ash containing 15–20% Ni; (2) a leaching step; and (3) purification. That whole flowsheet has been thoroughly investigated, and the processes scaled up to the pilot scale. Another strategy is presented here, consisting of recovering Ni without burning the plant. Ni can be extracted from the dry plant by water leaching, but the leachate is a multi-element solution from which Ni has to be separated. Selective precipitation of Ni hydroxide is not possible since Ni is bound to organic ligands. In this work, the plant leachate is processed by adsorption on the chelating resin DOWEXTM M4195. The results showed that Ni was selectively retained whereas the other main cations were not. Nickel could be recovered at the elution step. This methodology needs to be further investigated but these initial results are very encouraging and open the possibility of Ni recovery by agromining.

By C. Damiani

The Chuquicamata smelter, operating since 1952, has gone through several developing stages which have been characterized by the addition of peak technology for copper concentrate smelting (Teniente converter and Outokumpu flash furnace) with an intensive use of technical oxygen, which has permit-ted to partially discontinue the reverberatory furnace utilization. This paper shows the main indicators and operational practices at present, as well as those concerning maintenance aspects. Finally, the most relevant topics related to the future development of the smelter are mentioned with special remarks on the Decontamination Plan, which allows US to keep the high level of production, reducing the emission of contaminants according to the legal requirements in force.

Jan 1, 1993

By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting. lime roasting. is being tested for retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04). oldhamite (CaS). calcium sulfite (CaS03). hematite (Fe2O:J), magnetite (Fe304). and minor amounts of pyrrhotite (Fe1.xS) and pyrite. At 600°C. 650°C and 700°C. the main constituents are anhydrite. oldhamite. and hematite. At 750°C. 800°C. and 850°C. anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides. calcium sulfite. hematite. and minor oldhamite. magnetite. and pyrrhotite. At 650°C. 700°C, 750°C. and 800°C, anhydrite, oldhamite. arsenic sulfides, and hematite are present. At 850°C. the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CIM) in the determination of the calcium-sulfur-oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RIM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1991

By Kenneth L. Nash

The control of solubility of waste actinide ions, by conversion to highly insoluble mineral phases has been demonstrated in the laboratory. Actinide metal ions are removed from neutral pH solutions by a combined ion exchange-decomposition-mineralization process based on the application of the naturally-occurring hydrolytically unstable.polyphosphate organic compound phytic acid.

Jan 1, 1999

By J. Howarth

Two electrochemical processing methodologies have been used to electrogenerate bromine-laden solutions for gold-leaching purposes. In the first process, a laboratory-scale cell in which the anode and cathode compartments were separated by a cation-exchange membrane was employed. The bromine produced by electrolysis of a 4% bromide solution was used to leach gold from a low-grade ore. The pregnant leach solution was then returned to the cell to recommence the cycle. High current efficiencies (90-93%) were maintained over six cycles. In the second process, an undivided hypochlorite generating cell (Chloropac"') was used to generate bromine from a simulated leach solution. Electrolyses were performed on a pilot-scale (100-150 gallons) with solutions containing different levels of bromide ion. The current efficiencies were also high (80-90%) and unaffected by the bromide concentration (over the range 2.5-5%) provided the electrolysis was run to low conversion « 15%). The Chloropac module was capable of delivering 0.6 kg bromine per hour at a power cost of $0.09 per kg. Using these figures, a detailed economic assessment for a 1000 metric tonnes (MT) per day gold ore processing plant was made. Electrolytic regeneration of bromine in a gold leach/recovery circuit dramatically improves the process economics over cyanidation.

Jan 1, 1991

By Xiyun Yang, Hui Xu, Xichang Shi, Xiang Xiao

"Rod-like magnetite particles were prepared by precipitation of iron salts with urea under the induction of magnetic field. Temperature and initial Fe3+/Fe2+ ratio have a significant effect on the composition of the product. Magnetite particles change from spherical into rod shape in the presence of a 0.35 T magnetic field, The addition of a small amount of spherical seeds increases the rod-like magnetite particles yield. The seeds are prepared by aging ferrous and ferric solution with sodium hydroxide as precipitator. The aspect ratio of the rod is controlled by varying the volume ratio of seed to iron salt.IntroductionMagnetite, an important member of magnetic materials, has attracted a lot of attentions for its super magnetic properties. The rod-like magnetite particles have high anisotropy and coercive force as well as super magnetic properties compared to other shapes, and are widely used as high magnetic density media, magnetic devices and microwave materials [1-4]. Recent studies have found that magnetic field can direct magnetite growing along easy magnetization axis to get one-dimension particles [5-6]. Chen et al. [7] synthesized single crystalline nanorod magnetite under magnetic field. Wang et al. [8] discovered that magnetite grew along easy-magnetization directions under 0.35T magnetic field. Vereda et al. [9-1 O] found that magnetic field had a dramatic effect on the morphology, inducing the aggregates to line along one direction to form rodlike particles.At present, most of the synthesis methods reported in the literature result in a low yield of rod particles and the aspect ratio are difficult to control. Recently, we developed a seed-mediated growth approach to making rod-like particles in an aqueous solution. The spherical magnetite generated by oxidation serves as a seed. These seeds are then added to a solution containing iron salt and urea, and provide nucleation sites for magnetite rod growth."

Jan 1, 2011

By Milton Blander

A review of concepts and theories for predicting thermodynamic solution properties of multi- component high temperature liquid solutions is reviewed. During the last 50 years the ability to predict :such properties for molten salts, silicates and metals based on the generally known properties of the lower order (often binary) systems has been developed and shown to provide predictions which are quite useful in science and technology. There are many gaps in our understanding of these high temperature solutions, especially for metals, and considerably more work is needed.

Jan 1, 1996

By Shengli Wu, Mingyin Kou, Laixin Wang, Zhe Wang, Xinliang Liu

The sticking behavior of iron ores in the shaft furnace is one of the most important problems in the COREX melting progress, which directly influence the smooth operation and productivity of shaft furnace. Therefore, it is of great importance to study the sticking behavior of pellets in COREX shaft furnace. The results showed that porous metallic iron produced at the interface of pellets samples was the main reason for the sticking of pellets in the COREX shaft furnace. The SI (sticking index) and metallization rate increased with the reduction temperature and gas flow, and decreased with melting rate. However, the SI of pellets in the COREX shaft furnace could be decreased by the proper match of melting rate and reduction temperature, reduction temperature and gas flow, while the metallization rate of pellets were kept at a certain level. Furthermore, the matching of melting rate and reduction temperature was more effective than the matching of reduction temperature and gas flow.

Jan 1, 2016

By Andre L. De Vegt

Hydrogen sulfide is an expensive chemical used in nickel, zinc and copper mining and metallurgical operations for selective recovery and concentration of metals, from leach water streams, acid plant blow down streams, refinery electrolyte bleeds and precious metal, plant bleeds. Hydrogen sulfide is either produced on site by catalytic reduction of elemental sulfur or transported to the site as liquefied hydrogen sulfide (H2S) or as a sodium sulfide solution (NaHS) Biologically produced hydrogen sulfide has economically very interesting, application possibilities in the mining and metallurgical industry. Converting sulfates from waste streams into usable hydrogen sulfide by biological reduction results in operational cost savings in existing lime treatment systems. H2S can be produced biologically for less-than $500/ton S. For the past ten years Paques has been engaged in the development and installation of treatment systems based on biotechnological processes to remove sulfur compounds from water, air and gaseous streams. Paques has designed and installed a groundwater treatment system for the Budelco zinc refinery in the Netherlands to remove sulfate and heavy metals. The hydrogen sulfide produced is used for recovery of metals,, mainly zinc, from the ground water stream. The system has been operating since May 1992 treating a flow of 5000 m3/d. At Kennecott's Bingham Canyon Utah copper mine, a pilot plant started operation in November 1995 to develop the process for selective recovery of copper from leach water using biologically produced hydrogen sulfide from sulfate containing groundwater. Other pilot plants are operated at DOE's Pittsburgh Research Center and at Cominco Research focusing on selective recovery of metals.

Jan 1, 1998

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

By Andreas Siegmund

During the decade of the nineties the conventional method of primary lead smelting (sinter machine/blast furnace) was successfully challenged by the introduction of novel direct and continuous smelting processes. In combination with a significant shift in market structure, as well as more stringent government regulations these modem technological innovations like the QSL, Kivcet, and Isa/Ausmelt processes became more than major competitors. They have proven to be economically and environmentally viable. The intensification of the metallurgical reaction by applying oxygen enriched or pure oxygen bath or flash smelting principles resulted in cost savings and a higher flexibility with respect to raw materials and additives usage. By synchronizing individual auxiliary plant sections with the smelting process a virtually waste- free production and low-emission mode of operation with nearly optimum energy exploitation is achieved. The primary lead industry will gradually substitute the sinter -blast furnace operation with novel high-energy efficient technologies in the new millennium.

Jan 1, 2003

By Valery Kaplan

Sulfur emission in the form of SO2 in flue gases is one of the most serious atmospheric pollutants associated with coal combustion and non-ferrous metals production. The carbonate eutectic method for removing SO2 from flue gases at 723–923 K was initially proposed in the 1970s but despite its great efficiency (SO2 concentration in the flue gas after purification reached 0.003 volume %), it could not be implemented by industry due to the complexity of the carbonate melt regeneration stage. Earlier we proposed a method suited to coal-firing power stations where the melt was regenerated using CO as a reducing agent. However, most metallurgical plants do not use coal and therefore lack a large source of CO. Here we propose a method for removing sulfur from the carbonate eutectic melt by purging it with natural gas or a natural gas/air mixture, which are available in the vast majority of metallurgical plants. This reaction leads to the reduction of sulfate to H2S gas that leaves the melt. The experiments we conducted show that nearly complete sulfur removal from the melt is possible at 823 K and that the reaction rate is sufficiently high for a large scale process. One can foresee that this carbonate melt-based SO2 removal technique may become a practical and economically attractive method for limiting sulfur emission to the atmosphere from non-ferrous metallurgical processing plants.

By Seyed Ahmad Jenabali-Jahromi

In this paper a meshless method called Finite Point Method (FPM) is developed to simulate the solidification process of continuously cast bloom steel in both primary and secondary cooling region. The method is based on the use of a weighted least-square interpolation procedure. A transverse slice of bloom as it moves with casting speed is considered as computational domain. The two dimensional heat transfer equation together with temperature dependent thermophysical properties is solved in the computational domain. The present work is verified in the mold region by the comparison of the surface temperature simulated by FPM and finite volume method (FVM) and also comparison of solidified shell thickness simulated by FPM and measured on a breakout bloom. For secondary cooling region the validation is done by comparison of the surface temperature simulated by FPM, FVM and thermovision measurements.

Jan 1, 2009

By K. Nona C. Liddell

There is a significant amount of early work that has been largely forgotten that deals with the validity of the pseudo-steady approximation for liquid-solid reactions. Much of this was originally published in the chemical engineering literature but is highly relevant to hydrometallurgical processes. The purpose of this paper is to summarize some criteria that were been developed by various authors for determining the error associated with use of shrinking core models for liquid-solid systems.

Jan 1, 2002

By A. Mezei

Samples of cobalt and bismuth concentrates produced from the NICO deposit in Northwest Territories were subjected to a comprehensive metallurgical testwork consisting of: pressure oxidation, ferric chloride leach and carbon in leach, to recover the cobalt, bismuth and gold, respectively. A specific testwork program was designed to allow for the optimization of process parameters under multiple restrictive criteria. The overall objective was to establish leaching sequences that could produce acceptable recoveries while generating environmentally disposable residues as well as solutions suitable for further processing. The recoveries for the leaching stage, under the optimum conditions, were 97% for cobalt and 95% for gold, in the case of the cobalt concentrate. The bismuth concentrate produced recoveries of 99% for bismuth, 99% for cobalt and 97% for gold, respectively

Jan 1, 1999

By Jose R. Parga

In mining operations, cyanidation is the ,predominant method by which gold and silver are recovered from their ores and it is recognized that cyanide consumption can be a major factor that contributes to the operating costs for such operations. Also after extraction and recovery of precious metals a certain amount of cyanide is delivered to the tailings pond and must be considered with respect is environmental problems due to the toxicity of cyanides. In this regard, the Air-Sparged Hydrocyclone (ASH) has been used as a reactor for the treatment of cyanide solutions in two ways; first for cyanide recovery by acidulation using the Mexican modification of the Mills-Crowe process and second for cyanide destruction by oxidation with the use of chlorine dioxide (ClO2). In both cases, excellent performance can be achieved using the high capacity ASH system.

Jan 1, 1998

By Yosry Attia

Recent emphasis on environmental effects and costs of conventional mining processing, plus success in accelerating bacterial action, suggest that biotechnology be explored for gold ore processing. In our paper, the past experience with organisms in processing gold is reviewed. The use of microorganisms for liberation of gold from sulfide ores as a substitute for fine grinding is discussed. The possibility of accumulation of gold from solutions, such as cyanide solutions, is explored as a potential replacement for such processes, such as carbon-in-pulp or ion exchange. The improvement in engineering technology and kinetics needed to scale-up from laboratory experiments to production scale are outlined.

Jan 1, 1985