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By Y. Z. Zhang

Electrochemical oxidation of arsenopyrite in ferric sulphate media in the absence and presence of bacteria T jerrooxidans has been investigated for the purpose of understanding the dissolution chemistry of arsenopyrite and the bacteria attack mechanism. Mixed potential, polarization resistance measurements, polarization curve, cyclic voltammetry experiments were conducted in a ferric sulphate medium of 10g/L FeH, temp.25-35°C, pH 1.5-2.5 in the absence and presence of bacteria Tjerrooxidans, respectively. For the anodic process, a two-step reaction sequence is suggested by the electrochemical measurements. The initial step at a low potential is described by:

Jan 1, 1996

By Shu-cai Zhou

"To understand the solidification behavior of austenitic heat-resistant stainless steel (TP34 7) in rotary electromagnetic-field, the influence of electromagnetic stirring in mold (M-EMS) on solidification structure of TP34 7 heat resistant steel in a round billet continuous casting was investigated based on industrial experiments. The results indicate that the excellent billet solidification structure of TP34 7 heat resistant steel can be obtained with appropriate electromagnetic stirring parameters. The solidification structure of TP34 7 heat resistant steel can be remarkably refmed, central porosity and shrinkage cavity can be remarkably decreased and equiaxed grains zone widens was enlarged. The industrial trials verify that the stirring intensity of TP34 7 heat resistant austenitic stainless steel should be higher comparing with plain carbon steel. Due to a higher viscosity, rotating speed of molten stainless steel was 20-30% lower than that of molten carbon steel in the same magnetic flux density.IntroductionIn recent years, the development of ultra super critical (USC) plants is accelerated by the demands of environment protection and energy saving, and USC plants with steam temperature and pressure conditions in excess of 593°C and 24.lMPa respectively were constructed. To achieve the goal, it is important to develop new materials with excellent high temperature strength, superior resistance to oxidation and corrosion at high temperature. Besides, their cost must be low enough to meet the requirement of plants [ 1]. TP34 7H steel is promising austenitic heat-resistant steel, which is used as superheater/reheater tube material and is extensively used for high temperature components and fossil-fired power plants, and suitable to be used in USC boilers plant. This kind steel contains with about 0. 7%Nb and it keeps higher allowable stress and creep rupture strength than TP304 and TP321H [1-2]. TP347H has conventionally been produced by ingot casting followed by forging and rolling. Recently, in order to decrease the production cost, challenging trials to produce these types of alloys by a continuous casting (CC) process have been attempted. However, the solidification structure of austenitic stainless steel is one of the key issues that attract more attention. Due to the low thermal conductivity of TP347H heat resistant stainless steel (much smaller than that of plain carbon steel), pronounced defects during continuous casting of austenitic heat-resistant steel such as coarse columnar, center porosity and coarse bridging, greatly influence mechanical properties of fmished products.A widely used technique in metallurgy is the inductive drive of molten metals using rotational or traveling magnetic fields. Recently, rotary electromagnetic stirring (EMS) has been applied to reducing various defects and improving increase the solidification structure of the metals in the continuous casting of steel, Al-based alloys and Mg-based alloys [3-8]. Electromagnetic stirring of plain carbon and low alloy steel in the continuous casting bloom and slab is well established for improving the quality of cast products [9-11] and is widely used in industry. However, very few literatures on electromagnetic casting of heat resistant stainless steel have reported. In this work, an industrial plant trial was performed to clarify the effect ofM-EMS on the macroscopic quality ofTP347heat resistant steel billet, in which the regularity and mechanism of the influence of EMS on solidification casting billet were discussed."

Jan 1, 2014

Achieving continued economic growth with social equity within the natural limits of the Earth's 'eco-systems is the major issue facing the world today. The material and energy needs of the world cannot be met with the current ways of addressing this issue. The need for metals, an important class of materials, will continue into the future because their unique properties make substitution by other materials impossible in many applications and this need will continue to be met from primary metal production and recycling. However, the recycling rate will increase and the usage pattern of metals will change to reflect the environmental impact of their production and use. Pyrometallurgy has an important role in meeting the metal needs of the future since some metals can only be produced pyrometallurgically; the energy required to produce some metals pyrometallurgically is significantly less than by other methods; most metals are most efficiently recycled pyrometallurgically; and the release of harmful and toxic elements into the biosphere can sometimes best be controlled through pyrometallurgical processing. The development of strategies for pyrometallurgical processing for the future lies in the recognition that sustainable development calls for large step improvements in value delivered per unit of environmental impact over the entire supply chain. Pyrometallurgists can respond to this challenge by contributing to reducing the environmental impact of meeting metal needs using three broad strategies: "end-of-pipe" approaches to convert emissions into benign materials for storage or disposal; flowsheet redesign to limit or eliminate emission production; and improved recycling technologies. A number of examples are discussed to illustrate how the sustainability driver is already influencing the technological development of pyrometallurgical processes, and how these will develop further as the sustainability driver strengthens.

Jan 1, 2003

By Allan MacRae

Freeport-McMoRan Inc. operates an ISASMELTTM furnace for the smelting of copper concentrate at the Miami Smelter in Claypool, Arizona. In May 2017, the furnace was restarted after incorporating newly designed copper cooling elements from just above the tap hole to the underside of the roof. The objective of the improved cooling design was to extend campaign life by eliminating existing failure mechanisms with the wall refractory. In addition to upgraded bathline coolers and complete coverage of the gas offtake transition, or ‘kettle’, with plate coolers, a novel arrangement of coolers was installed in the remaining freeboard area. The shell required significant cutting and re-stiffening, as well as extensive modification of the cooling water piping. Based on performance observed to date, it is expected that smelter throughput will be increased due to extended ISASMELTTM refractory campaign life.

By S. Viswanathan, Q. Han, A. S. Sabau

"In spite of recent advances in the mathematical modeling of fluid dynamics for materials processing applications, no significant advances have been made in the numerical discretization of these equations. In this work, the application of two-step projection methods for the numerical simulation of interdendritic flows is discussed. Unlike previous methods, the methods presented here are constructed for the exact equations which are characterized by variable density and volumetric fraction of the liquid. The drag terms, which describe the momentum loss due to the flow around and through the dendrite structures, are treated implicitly. Numerical examples for shrinkage-induced flow during solidification of an Al-4.5% Cu alloy bar is used to illustrate the effectiveness of the proposed algorithm.IntroductionLiquid contraction during solidification plays an important role in the formation of casting defects such as shrinkage voids, microporosity, and macrosegregation. Owing to their importance, the study of transport processes during solidification have received considerable attention during the past years [1, 2]. By the use of volume-averaging techniques, the mass and momentum equations for flow through a stationary dendritic structure were derived [3]. By using the volume-averaging techniques for multi-phase systems, two-phase transport equations for solidification problems were derived [4]."

Jan 1, 1999

By Kotaro Ogura

"The electrolysis process in which CO2 is selectively reduced to C2H4 at a three-phase(gas/solution/metal) interface on a copper-mesh electrode has been developed in a concentrated solution of potassium halide. At open-circuit potential, CO2 is captured on the electrode by being inserted into the double-layer consisting of halide anions specifically adsorbed and potassium cations which are located in the Helmholtz inner and outer layers, respectively. CO2 thus activated is subjected to the electrochemical reduction. In the early stage of reduction, CO2 is converted to formate radicals that are adsorbed on the electrode by taking the place of halide anions. The reductive coupling of these radicals results in the formation of intermediates such as -CH2C(O)- and CH2=CH-, and C2H4 is finally produced. The catalytic activity of the electrode process involving the insertion of CO2 into the double layer is not deteriorated at all during the electrolysis, and the continuous reduction of CO2 to C2H4 is possible with the addition of inorganic acid under the assistance of natural energy.Carbon dioxide is a serious pollutant released from fossil fuel power station, internal combustion and many industrial operations. The easy release of CO2 to the air has caused the global warming, and the technique which intends to curtail CO2 by pushing it back into the ground has been suggested. However, this problem should be greatly mitigated if CO2 can be converted to innocuous substances. Especially, the reuse of CO2 as fuels and chemicals is extremely effective not only for the mitigation of the global warming but also against the depletion of the fossil fuel reserves. Several processes for converting CO2 to valuable compounds have been proposed including hydrogenation over heterogeneous catalyst at high temperature and electrochemical and photochemical reduction. In the conversion and cutback processes of CO2, however, it is of importance that the process is feasible under mild conditions, because the secondary generation of CO2 is feared if high energy is required and supplied with a fossil fuel. In this meaning, the electrochemical reduction of CO2 taking place at room temperature, which is similar to photosynthesis, is promising. From the practical point of view, it is further necessary that the conversion rate is high enough and the product is satisfactorily valuable."

Jan 1, 2008

By David G. Dixon

Although the kinetics of leaching processes are of paramount importance in the design and analysis of nearly all hydrometallurgical flowsheets, these concepts remain poorly understood and, as a result, are only rarely applied to mass and heat balance models. In this second of two papers, we demonstrate how simple yet powerful models of leaching kinetics and other rate processes may be added to mass and heat balance models, and apply these concepts using a spreadsheet model of a simplified pyrite autoclaving flowsheet. In particular, we focus on the interpretation and scale-up of batch leaching data, and on simple means for modeling other phenomena commonly associated with leaching, such as reagent depletion, gas-liquid mixing, and the precipitation of oxides and basic salts.

Jan 1, 2002

By R. Craig McClung

Contrary to other sulfide minerals, where recovery is principally liberation controlled, the recovery of molybdenite is more complex. It is this complexity that initiated a geometallurgical investigation of molybdenites from Bingham Canyon. The aim of this investigation was to determine the effect mineralogy and/or mineralogical attributes have on recovery. All samples were analyzed using normal mineralogical techniques. The results reveal the presence of two distinctly different types of molybdenite. These have been identified as the two polytypes of molybdenite: i.e. hexagonal (2H); and rhombohedral (3R). The 2H-polytype occurs as textbook-shaped particles in quartz-molybdenite veins that are located in the current pit bottom. The 3R-polytype occurs as disseminated, “ball”-shaped particles with a dull or frosted appearance and are concentrated along the margins of the current pit. Concerning their metallurgical behavior, each type exhibits unique metallurgical properties that are consistent with those reported in the published literature. The 2H-polytype is easily ground and kinetically “faster” floating with surface attributes that are amenable to higher rates of recovery. This results in the production of a high quality concentrate under normal operating conditions. The 3R-polytype, by comparison, is difficult to grind and kinetically “slower” floating with surface attributes that are less amenable to recovery. Therefore, in deposits with higher concentrations of the 3R-polytype, modifications to the normal operating parameters may be necessary to improve recovery. This investigation highlights the necessity for understanding the mineralogical characteristics of any economic mineral(s), as these will have a direct impact on recovery.

By Isadora Dias Perez, Monica M. Jimenez Correa, Jorge A. Soares Tenorio, Denise Crocce Romano Espinosa

The generation of mining waste has been the subject of environmental, economic and social concern. Alternative and sustainable methods of recycling metals technologies are desired. The present work focuses on the application of the ion exchange technique for the extraction of metals contained in a lateritic nickel mining effluent. The Purolite S950 chelating resin was used in the present work because it has the ability to adsorb transition metals present in an acidic solution. The experiments were carried out in a batch varying the pH in the range of 0.5–2.0. 1 g of resin was placed in contact with 50 mL of solution and stirred for 120 min at a speed of 200 rpm and temperature at 25 °C. The results demonstrated that the affinity of the resin varied with pH. The adsorbed metals were only copper, manganese, magnesium and zinc. The most extracted metal was copper, corresponding to 37%, when the solution was conditioned at pH 2.0.

Mar 1, 2018

By Yan Zeng

Lithium metal silicates (Li2MSiO4, M = Fe or Mn) composed of abundant and non-toxic elements are important cathode materials for Li-ion batteries (LIB). In contrast to solid-state or sol-gel methods, hydrothermal synthesis conducted in pressure reactors is a favorable processing route as it provides the potential for scalable production and is environmentally benign. However, the key is to control the precipitation reaction to obtain powders with desired properties to meet battery specifications. Through a systematic study, we have found that Li2MSiO4 with tunable size from 300 nm to 1.5 μm can be produced by adjusting precursor concentrations, temperature, and reaction time. Under optimum conditions, high purity Li2MSiO4 with minimum defects were successfully produced and examined as an LIB cathode. The use of complexing agents promoted the formation of unique hollow particles via the self-assembling of elongated crystals. A four-step formation mechanism is proposed based on extensive characterizations with XRD, HR-TEM, SEM, and Mössbauer spectroscopy.

By Arthur E. Morris

Fifty years ago when Professor Yazawa began his career, the field of process simulation and modeling was in its infancy. Since then, tremendous progress has been made in our ability to model metal production flowsheets from mine to refined metal. This progress has come about by parallel developments in basic understanding of process chemistry and in computational techniques, This paper will review the progress made in process understanding and modeling in lead, zinc, and copper metallurgy from its inception to the present, and the role of Professor Yazawa's work in furthering this progress. Specific examples will be given for the sintering of lead concentrates, slag fuming, zinc concentrate roasting, flash smelting of copper, and pyro-extraction of zinc. Factors limiting further progress will be described.

Jan 1, 2003

By Rodney Hundermark, July Ndlovu, Lloyd Nelson, Phillimon Mukumbe, Paul van Manen, Whitey Seyanund, Bart Pieterse, Bertus de Villiers, Diale Mokwena

The 2003 redoubling in power to 68MW on the Polokwane Smelter furnace represented a significant intensification in platinum group metal (PGM) smelting. Combined with onerous ‘green’ PGM concentrate smelting requirements, this yielded conditions unusually corrosive to copper coolers and refractories. This presented unexpected operational and design challenges to reliable crucible operation and maintenance. Combined with specific operational control intervention, development of protective coatings has led to the life of water-cooled copper components improving from 9 to 40 months. The furnace matte endwall was extended in 2010 to address accelerated wear of refractories and the potential risk for contact of copper components by superheated matte. An 18 month planned endwall rebuild cycle has been demonstrated (versus catastrophic failure within 9 months). Finally, benefits including lower energy consumption, improved metal recoveries and higher productivity resulting from operational and in-house design developments will be described, that justify “Celebrating the Mega-scale” in PGM smelting.

Jan 1, 2014

By Arthur E. Morris

Fifty years ago when Professor Yazawa began his career, the field of process simulation and modeling was in its infancy. Since then, tremendous progress has been made in our ability to model metal production flowsheets from mine to refined metal. This progress has come about by parallel developments in basic understanding of process chemistry and in computational techniques. This paper will review the progress made in process understanding and modeling in lead, zinc, and copper metallurgy from its inception to the present, and the role of Professor Yazawa's work in furthering this progress. Specific examples wi1\ be given for the sintering of lead concentrates, slag fuming, zinc concentrate roasting, flash smelting of copper, and pyro-extraction of zinc. Factors limiting further progress will be described.

Jan 1, 2003

By Minjun Tang, Jianfeng Zhou, Feng Chen, Linjiang Qing, Xiaolei Song, Yufeng Guo, Tao Jiang

"Reduction swellability index (Rsn and low temperature reduction disintegration index (RDI) of vanadium-titanium magnetite oxidized pellets are harmful to the processing of ironmaking, for example, causing serious gas permeability, decreased yield, higher coke ratio and more furnace dust. Thus, the improvements of RSI and RDI of vanadium-titanium magnetite oxidized pellets were investigated in this paper, including the pretreatment of raw material, additives of dolomite or boric acid, pellets treated in chloride solution and so on. The results showed that damp milling as pretreatment and boric acid added in pelletizing were conducive to the RSI which decreased 5% and 7% respectively, while they were not efficient enough in improving RDI. Dolomite was efficient in improving RSI, but had negative effect on RDI. There was no evidence to show that RSI and RDI would be improved when pellets were treated in chloride solution. Pursuing this further, the mechanism of those improvements were investigated.IntroductionIn the world, vanadium-titanium magnetite utilization is investigated around how to recover iron, titanium, vanadium, and divided into blast-furnace method and non-blast-furnace method according to respective characteristics. Blast furnace method [1, 2] can recover iron and vanadium effectively, but Ti02 cannot be recycled. Non-blast-furnace methods include rotary kiln-electric furnace method, pre-reduction electric furnace method, reduction- grinding method and sodium vanadium-rotary kiln-electric furnace method and so on. [3-7]Comparing to the Non-blast-furnace method, the method of blast furnace smelting has been put into industrial applications. And it has the following advantages: First of all, effective recycling iron and vanadium; Second, technical problems of high titanium slag in blast furnace smelting; Third, it has mature technology in blast furnace smelting."

Jan 1, 2013

By Giacobbe Braccio, Alessandro Blasi, Assunta Romanelli, Massimo Morgana, Corradino Sposato

The solvent extraction technique is the only industrial way used to separate and purificate yttrium from other rare earths. In order to improve this process several extractants have been tested during last years. In this work, the behavior of sec-octylphenoxy acetic acid (CA-12) in Yttrium recovery from high concentrated heavy rare earth mixture was investigated. Sodium hydroxide solution was used in order to presaponify organic phase composed by CA-12 and Tributyl phosphate (TBP) diluted in kerosene. In the investigated condition, TBP confirmed its role of phase modifier not significantly altering the extraction behavior of CA-12. The CA-12-TBP system showed a high affinity in extraction for lighter rare earths such as Sm, Eu, and Gd, leaving yttrium in aqueous phase. Using a feed concentration (P [RE]) of 1 M, organic mixture is capable to extract around the 70% of metals in a single extraction test showing this extraction sequence Y < Lu < Yb < Tm < Er < Ho < Dy < Tb < Gd < Eu < Sm. Moreover for [CA-12] = 1.79 M and [RE] = 2 M the instability of extraction system occurs.

Mar 1, 2017

By Ling-yun Yi, Yuan-bo Zhang, Bing Hu, Zhu-Cheng Huang, Zhen-yuan Liao

"Nucleation and growth mechanism of iron crystal grain in coal-based shaft furnace direct reduction process by microwave heating were investigated by optical microscope, scanning electron microscope and EDX. The results indicate that microwave has selectivity on various minerals which absorb microwaves. The high temperature in certain area of pellets and thermal stress on the interface of minerals are formed, results in the wustite grain smashed along the joints, and iron crystal grains turned out a spherical shape obviously. The iron crystal nucleus is formed firstly at the edge of wustite, on the interface between grains and in the holes in pellets, and grows gradually while reduction carries on from surface layer to inner core. Microwave heating promotes the rate of transportation and accumulation of the iron crystal grain, increases growth rate of iron crystal grain and contributes to formation of dense iron-jointed crystal texture eventually.IntroductionMicrowave energy as a new energy, which selectively heating materials through internal energy dissipation, has the advantages of heating uniformity, high thermal efficiency, fast heating, clean and pollution-free compared to conventional heating motheds. Microwave energy also has obvious superiority in increasing productivity. Thus, it has been widely used in many areas, including electronics, food processing, chemical, medicine, environmental protection, and family life etc [1]. As a rapidly developed green metallurgical method, microwave heating also has been widely recognized by areas of grinding, pretreatment, pre-reduction, drying, furnacing, metal extraction, and waste materials processing and utilization. Some research achievements are gradually putting into practice, showing great potential in chemical and metallurgical industry [2-3]."

Jan 1, 2011

By Fuqiang Guo

Scorodite (FeAsO4, 2H2O) is suitable mineral carrier for immobilization of arsenic-rich wastes. Its stability is, however, highly pH dependent (typically at 4 ≤ pH ≤ 7) and satisfactory only under oxic disposal conditions. In thiswork an encapsulation process using mineralized gels of aluminum hydroxy-oxides is developed to enhance the stability of scorodite under wider pH and redox potential range conditions. The encapsulation involves blending and ageing of synthetic scorodite produced by McGill’s atmospheric scorodite process with aluminum hydroxyl gels derived from controlled hydrolysis of aluminum salts. The amorphous hydrolyzed Al-gel encapsulates the scorodite particles,which upon short-term aging transforms into crystalline Al (OH)3/AlOOH mineral phases providing a robust protection microscopic barrier. Long-termstability testing demonstrates the encapsulation systemto be highly effective in suppressing arsenic release under either oxic or anoxic (100 mV < Eh < 600 mV) potential and neutral-alkaline pH (7 ≤ pH ≤ 9) ranges.

By Arthur W. Cooper

This paper contains a review of the development of blast furnace? slag handling and processing technology in the Ironmaking industry over the past 30 years, with an emphasis on economic and environmental factors. The requirements and practice of air-cooling slag for use as aggregate and of pelletizing and granulating slag for use in cement manufacture are described. The operation of slag pits, slag pots or ladles, the slag pelletizer and early granulation systems are compared with the new continuous .granulation, dewatering and handling systems developed in the past decade.

Jan 1, 1992

By P. Kerr

Iron segregation is pre-dated by copper and nickel segregation processes for which the experimental methodology and reaction chemistry were established. The accepted reaction sequence for segregation involves the generation of hydrogen chloride, the chloridization and volatilization of the metal chloride, and precipitation of the metal from the metal chloride in the vicinity of carbon. Iron segregation roasting offers a potential extraction solution for processing oxide deposits with complex mineralogy or waste streams such as Minette-type iron deposits, nickel laterites, ilmenite, red mud, electric arc furnace (EAF) dust, mill scale and slag. After subsequent magnetic separation, one is left with a high grade metallic iron powder which can be marketed for powder metallurgy or briquetted to serve as a direct reduced iron (DRI) product. The non-magnetic product is typically concentrated oxides including rutile, alumina, or oxides of V, P, and rare earths, etc. that may be economically recoverable with subsequent processing. While operating conditions vary for different metals, they share the requirements of an elevated operating temperature and a mixture of oxide ore, carbonaceous additive and a chloride additive in varying amounts all in a closed reactor to allow for reducing conditions and contain the volatile chlorides. This process is then followed by some form of physical separation. Testwork performed by the authors shows promising results that may aid in future development of the process. Segregation roasting of iron will likely never displace traditional beneficiation and ironmaking technologies; however, it has great potential in niche markets where traditional technologies have failed or current technologies generate substantial waste.

By Yoon-Bong Hahn

A mathematical model has been developed to analyze and predict the reduction process of iron ore particles in a two-stage fluidized bed system. This model includes the effect of particle degradation to elucidate its effect on reduction of iron oxides. Although the particle degradation is dependent on kind of iron ores, it was found that eighty to ninety percent of overall degradation is occurred in the prereduction stage mainly due to thermal stress and volume expansion. The degradation of particles in the?final stage is not much, but is mainly due to interparticle collision and abrasion. It was also found that to obtain a target reduction degree, it is of great importance to control the bed temperature and the residence time of paarticles in R1 rather than in R2. Optimum range of residence time was 15-20 minutes in the prereduction stage; 30-35 minutes in the final reduction stage.

Jan 1, 1996