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By Zhihong Liu

Monodisperse micron size nickel oxalate particles with rhombohedron morphology were prepared from condensed Ni(OH)2 suspension by a novel gel-sol process proposed by one of the authors. Firstly, condensed nickel hydroxide gel was formed by fast adding 1 mol dm-3 NaOH solution into 0.2 mol dm-3 nickel chloride solution, and then oxalic acid solution with a concentration of 0.25 mol dm-3 was dropped into the gel drop wise through a pump equiped with a pH controller under preset pH value, and in this process, Ni(OH)2 gel was converted gradually into monodisperse nickel oxalate sol. The formation of the nickel oxalate particles was found to proceed through a dissolution-recrystallization mechanism from the nickel hydroxide gel. The product particles exhibited rhombohedron like shape with micron size long axis and sub-micron size short axis. The effects of such factors, as temperature, surfactants, et al, were evaluated experimentally on the particles sizes and morphologies.

Jan 1, 2006

Sodium is added to aluminum-silicon eutectic alloys to modify the structure. The ideal amount is about 100 ppm but due to the fact that sodium is lighter than aluminum and can float to the surface where it bums, oxidizes ad volatilizes, a far greater amount is usually added. Furthermore, as the sodium is continually lost from the alloy the optimum amount is only present for a limited time. The net result is a process which is hard to control, produces fumes and a considerable amount of dross. It is shown that by electrochemically titrating sodium through a tube of sodium beta alumina electrolyte that the sodium can be added continuously in a controlled way. As the sodium is added to the bulk of the aluminum, there is no sodium on the surface of the alloy so that little surface oxidation occurs, and no fumes and dross are produced. This leads to an improved product and working conditions.

Jan 1, 1995

By Peter Willbrandt

Norddeutsche Affinerie's routes date back to the 18th century. NA was established in 1866 as a joint stock corporation. NA's core business covers the production of copper cathodes from primary and secondary raw materials and the processing of them into wire rod and shapes. Part of the shapes are processed into pre-rolled strip and shaped wires within the Group. With some 3,200 well qualified and highly motivated employees, the NA Group produces some 560,000 tonnes of copper cathodes, 370,000 tonnes of wire rod, 230,000 tonnes of shapes, 130,000 tonnes of pre-rolled strip as well as 70,00 tonnes of strips and shaped wires annually. NA's product range is complemented primarily by precious metals, selenium, sulphuric acid, lead and nickel sulphate. The paper will give an insight into the performance of NA and its business units with regard to production, environmental and health protection and occupational safety.

Jan 1, 2006

By Ashok D. Dalvi

Production of nickel from laterite ores has occurred for over 100 years beginning with processing of garnieritic ores from New Caledonia. However, until now the world nickel supply has been predominantly from sulfide sources. Going forward, the authors project that the production of nickel from sulfide ores will remain more or less constant. Most of the expansion in nickel production capacity over the next ten years will come from processing of laterite ores. Thus the capital and operating costs of new laterite projects will have significant impact on the nickel supply and therefore price. The authors have reviewed the history and capital and operating costs of various recent laterite projects and capital and operating costs of these projects and those "on the drawing board". The authors have also evaluated the risk associated with such projects. The paper will discuss the impact of this and the recent history on the future development of laterite nickel projects.

Jan 1, 2004

By J. W. Whitney

Itronics Inc., through its wholly owned subsidiary Itronics Metallurgical, Inc. (IMI), has successfully developed technology that allows it to be fully integrated as a photochemical recycler. IMI is now using this technology to expand its regional operation, which collects used photographic chemicals, chemically removes 99.997% of the silver and uses the residual to make a line of high quality liquid multinutrient liquid fertilizer products. Elevated silver discharges from the Reno-Sparks sewage treatment facility, that were traced back to incoming waste photographic chemicals and which were seriously impacting the sensitive fishery, provided the impetus for this project. This paper is updated from a paper presented at the Twenty-Second International Precious Metals Conference Toronto, Ontario, Canada in June 1998. It presents an overview of the scope of the problem solved by the technology, some of the permitting and development issues, and some of the specific fertilization formulations that are now being marketed.

Jan 1, 2000

By I. Sofia Fernandez del Rio

This paper describes a process for the treatment of the dusts generated during the operation of blast and reverberatory furnaces in the lead smelter, to remove zinc, cadmium, arsenic and halides from the circuit. The process consists of a Pefloles' developed leaching/purification stage and a solvent extraction process developed by Lurgi. The plant capacity is 5,000 tonnes Zn/year. The feed to solvent extraction contains 8 g/1 Zn. Impurities such as copper, iron, arsenic and cadmium are removed by conventional cementation processes. The cadmium product is 99.99 % pure. The solvent extraction process consists of two extraction stages, one washing stage and two stripping stages. D2EHPA is used as the extraction agent and 25% ammonia as the neutralizer. The rich-zinc solution is sent to the electrolytic zinc plant for zinc recovery. The raffinate produced, which is a mixture of ammonium sulfate and chloride, is used for agricultural applications.

Jan 1, 2000

By Corby Anderson

The efficient separation of palladium from the transition metals copper, nickel and iron can be effected by passing a leach solution of these metals through a column of the silica polyamine composite material, WP-1, patented by Purity Systems Inc (PSI), Assignee, University of Montana with exclusive license to PSI. The separation can be done at the intrinsic pH of a nitrogen species catalyzed (NSC) oxidative pressure leach solution (~0) and stripping of the palladium from the composite can be effected with hydrochloric acid/ammonium chloride solutions at 50oC. Batch capacities of the composite for palladium are ~ 1.8 mmol/g resin. The possibilities for isolating the metal from the strip are discussed. Given the proven longevity and rapid capture kinetics of the polyamine composites, this new approach should prove to be an economically viable alternative to the multi-step concentration processes practiced in the PGM industry to date.

Jan 1, 2003

By M. Ramprecht, M. Wu, A. Kharicha, A. Ludwig, H. Holzgruber

"The influence of the frequency of AC power supply on the magneto-hydrodynamic during the electroslag remelting process is studied. The focus is on the electrodynamic field and its resulting mechanical effects on the flow and liquid interfaces. The possible influence of the electrochemistry on the droplet formation is qualitatively discussed.IntroductionThe electroslag remelting (ESR) process is a secondary melting technique which can be used for a variety of metals and alloys, provided appropriate fluxes (slags) and melting parameters are employed. The ESR process is presently operating mostly with AC current of about 50 Hz. However for reasons primarily of inductive losses in the electric circuit, furnaces for ingots larger than 1 m, use or are projected to use current of very low frequency (< 5 Hz). Effects of lower frequencies (2.5-5Hz) on macrostructure and non-metallic inclusions were recently studied by Chang [1]. Most of investigations were performed either with DC power or with AC of 50-60 Hz [2-4]."

Jan 1, 2012

Over the years, numerous hydrometallurgical processes have been proposed as an alternative or complement to smelters for the treatment of copper concentrates. Most of these initiatives met with limited success. Bioleaching is applied commercially for secondary copper minerals heaps and dumps, and bacterial leaching processes are being developed for copper concentrates, although industrial application is still years away. More recently developed processes usually include pressure leaching and/or ultrafine grinding. This paper proposes a new leach process to treat copper sulphide ores or concentrates: the process operates under atmospheric pressure and uses limited concentrations of ferric sulphate as oxidant; the key to the process is the regeneration of the ferric ion, which can be effected in-situ (direct process) or ex-situ (indirect process) using SO2/O2. Examples are presented for the treatment of copper concentrates by agitation leach and of copper ores by heap leaching. Application of the process to copper gold ores and chalcopyrite concentrates is also discussed.

Jan 1, 1999

By P. A. Olubambi

The effect of ore mineralogy on the bioleaching of metals from complex sulphides was studied by investigating the bioleaching of zinc and copper from a bulk complex sulphide ore from Ishiagu, Nigeria, using mixed cultures of Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum in mechanically stirred reactors at varying particle sizes. Mineral phases within the varied particle sizes of -53, 53, 75 and 106µm were identified using X-Ray Diffraction (XRD), while the elemental distribution within the varied particles sizes was determined by X-Ray Fluorescence (XRF) and Optical Emission Spectrometry using Inductively Coupled Plasma- Optical Emission Spectrometer (ICP-OES). Bulk ore and the leached residues were examined by X-Ray Diffraction. The highest bioleaching recoveries were obtained at particle size of 75µm, while particle size of 106µm gave the least recoveries. Lower recoveries at particle sizes of 53 and -53µm were as a result of their higher silica and siderite content which affects pH, iron mobility and oxidation.

Jan 1, 2006

By W. Gong

Their outstanding thermal stability and high energy product make Sm(Co,Fe,Cu,Zr),-type alloys attractive for advanced applications. The near net-shape production of Sm(Co,Fe,Cu,Zr), bonded magnets make them potentially superior to any magnets made by sintering. Although pioneering work done by Shimoda et al. and other investigators provide insights on the proper compositions and process control of this alloy system, additional work is still necessary to improve our understanding of alloy behavior at various processing stages and to increase the production yield during powder processing. In this paper we report on the development of anisotropic Sm(Co,Fe,Cu,Zr), alloy powders for the bonded magnet application. Our focus is on the development of a moderate coercivity powder requiring a relatively low magnetizing field to charge the magnets to their optimum Br, Hci and BHmax. The magnetic properties are related to the evolution of the microstructure at various processing stages and the average particle size and size distribution of powders.

Jan 1, 1997

By Kim Fagerlund

A novel apparatus for studying refractory infiltration and dissolution/degradation under a temperature gradient was developed. To supersede conventional isothermal refractory testing, a new temperature gradient technique, based on a crucible equipped with a cooling element, has been developed to provide practical information on the penetration and dissolution of refractory materials under cooled conditions. This technique was adopted and applied to several refractory-slag systems. Commercially available magnesia chrome refractory bricks against a copper-containing calcium ferrite type of slag were tested and compared using both a conventional crucible test and the new temperature gradient method. The experiments were conducted at 1300-1420°C under a controlled atmosphere of nitrogen or air. It was noticed that the type of porosity has a significant effect on infiltration of magnesia chrome refractories. Furthemore, the copper-containing calcium ferrite slag caused a severe slag attack and refractory failure in some cases, due to its fluidity and corrosive nature.

Jan 1, 2002

By N. Solak

CrN, TiN and Ti-B-N coatings were deposited onto H13 hot-working tool steel and alumina substrates by arc-PVD. The coatings were characterized with respect to their mechanical and structural properties. Oxidation behavior of the coatings on alumina substrates was investigated by TG/DTA. Samples coated on H13 substrates were oxidized in a tube furnace under atmospheric conditions at specific temperatures determined from TG/DTA tests of the same coatings deposited on alumina substrates. The oxide scale morphology was characterized by scanning electron microscopy and X-ray diffraction. Oxide scale thickness change and TG data were used to calculate oxidation reaction activation energies. It was determined that boron addition into TiN coating improves not only mechanical properties but also oxidation resistance. Depending on the substrate material different oxidation activation energy values for the TiN and Ti-B-N coatings were determined revealing the importance of film morphology on oxidation resistance.

Jan 1, 2006

By Cevat Serdar Kucukkaragoz

The kinetics of prereduction of Chromite by carbon was studied under argon atmosphere at temperatures between 1000°C and 1300°C . The compacted and agglomerated specimens were reacted by using a TGA system. The mixing characteristics and the degree of compaction of the chromite and coke particles were the main parameters influencing the reduction kinetics. The reduction rate increased with temperature reaching to 81% reduction at 1300°C. The metallization started as the metallic nucleation around the particles which was first observed at 1100°C. The particles were surrounded by the metallic phase at approximately 40 % reduction obtained at 1200°C. At 1300°C, the reduction proceeded with a high rate during initial stages and with a low rate at final stages. The reduction was found to proceed in the sequence of Fe3+to Fe2+, Fe2+ to Fe(metal) and Cr3+to Cr(metal) with the formation of carbides.

Jan 1, 2006

By Jorge Gibson, P. Chris Pistorius, Megha Jampani

"The main reason for the significant carbon intensity of integrated steelmaking (approximately 1.8 tons of CO2 per ton of steel) is the use of carbon-based reductants in blast furnace ironmaking. Several changes to blast furnace ironmaking have been proposed as ways to reduce carbon intensity and cost. A conceptually simple two-zone blast furnace mass and energy balance can be used to quantify the expected impact of such process changes on coke rate, carbon intensity, and productivity. Examples to be discussed include top gas recycling, combining lower blast temperatures with increased coal injection to produce a rich top gas, using prereduced feed, and tuyère injection of natural gas. The use of the operating window – which illustrates how allowable flame temperatures and top-gas temperatures constrain feasible oxygen enrichment levels – is illustrated. Increased use of natural gas would lower the carbon intensity of blast furnace ironmaking.IntroductionBecause of the significant carbon intensity of steelmaking (approximately 1.8 tons of CO2 emitted per ton of steel produced) and the high production rate of steel (more than 1.4 billion tonnes per annum), steelmaking is responsible for a large percentage, approximately 6.7%, of world anthropogenic CO2 emissions [1]. By far the largest input of the carbon into conventional steelmaking is as coke, which is essential to blast furnace ironmaking. A typical fuel rate for blast furnace ironmaking is 450 kg of fuel per tonne of hot metal (THM). (""Fuel"" includes coke and injectants which partially replace coke; pulverized coal and natural gas are typical injectants.) Assuming the fuels to contain 90% carbon on average, and since nearly all of this carbon exits the steel plant as CO2, a fuel rate of 450 kg is equivalent to a CO2 intensity of 1485 kg/THM – by far the largest part of the total CO2 intensity of steelmaking.Blast furnace ironmaking is expected to remain the main source of new iron units; this paper gives some estimates of the extents to which further reductions in carbon intensity from blast furnace ironmaking is possible. A recent European assessment suggested that blast furnace process intensification options such as increased pulverized-coal injection or natural gas injection would yield only modest energy savings [2]. However, if the focus is on CO2 emissions rather than on total energy use, there would be an advantage to using fuels – such as natural gas – which have lower carbon contents relative to energy content."

Jan 1, 2014

By Patrick R. Taylor

Ilmenite concentrate and methane are fed to a non-transferred arc thermal plasma reactor to produce a powder that is primarily TiC and Fe. This material has promising characteristics for powder metallurgy applications. Free energy minimization plots were used to predict the feasibility of the reaction. An estimate of the optimum molar ratio between the ilmenite concentrate and methane was made based on the mineral composition. Argon-helium mixtures were used as plasma gases. The effects of power input level, carrier gas flow rate, powder feeding rate, and methane-ilmenite molar ratio were studied and the behavior of the system characterized. Two different powder injection angles were tried. A mathematical model to describe the temperature profiles in the reactor was formulated and solved. The product has been characterized by x-ray diffraction and atomic absorption. A conversion of 97 % of Ti to TiC was achieved. It was found that minor amounts of titanium oxides, iron carbide and free carbon are also present. TEM and SEM were used to study the morphology.

Jan 1, 1996

By S. P. Song

A computational methodology based on the coupled finite element and boundary methods is developed to predict the free surface shapes of electrically conducting liquids supported by the electromagnetic field. The work is an extension of our previous FEIBE model for induction calculations. The free surface algorithm is developed using the Weighted Residual Method, the very same used for nonlinear finite element formulation. This allows the treatment of field computation and free surface prediction in the same manner, thus making easier the formulation of the magnetically-supported free surface problems. Like other nonlinear algorithms, the boundary/finite element free surface scheme is also iterative owing to the fact that free surface shapes are unknown a priori. But the numerical scheme is robust and efficient and is capable of handling rather complex free surface deformations. Computational algorithms will be given and are tested by comparing with other solutions whenever available. Computed results of magnetically-supported free surface shapes are presented for magnetic levitation under microgravity and floating zone refining processes under normal gravity.

Jan 1, 1996

By Courtney A. Young

All cyanide species are considered toxic and can be found predominantly in industrial effluents generated by metallurgical operations. For example, cyanide&apos;s strong affinity for metals makes it favorable as an agent for metal finishing and treatment and as a lixivant for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent water contamination. Various methods of cyanide remediation by separation and destruction are available, but certain methods are more effective than others depending on the cyanide species being remediated. Photolytic destruction is regarded as the one technique that is independent of the cyanide species involved. The destruction of various cyanide species by several photolytic techniques has been investigated for the past few years. A literature survey suggests heterogeneous photocatalysis with anatase (TiO,) should behave similarly to homogeneous photolysis with hydrogen peroxide (H,O,) since proposed reaction mechanisms for both processes involve hydroxyl radicals. However, experimental evidence on a suite of cyanide species suggests otherwise. A new mechanism for the photocatalytic destruction of cyanides, especially SAD species, is therefore proposed.

Jan 1, 1998

By W. D. Riley

Engineered Scavenger Compounds (ESCs), developed by the U. S. Bureau of Mines I are a novel class of compounds that can selectively recover a desired element from &apos;a solid or molten alloy. Lithium titanate (Li2Tip7 or Li20&apos; 3TiO.) is being used as an ESC to recover lithium (Li) from Aluminum-Lithium (AI-Li) alloys. X-ray diffraction measurements have shown that lithium titanate undergoes a phase change from an orthorhombic structure to a hexagonal structure. This change is due to the incorporation of Li in the matrix of the material and the effect of temperature. Although both of the structures are metastable, the hexagonal phase that forms during the scavenging of Li from AI-Li alloys appears to be the more stable phase. Recovering Li from the ESC by electtodeposition does not cause the structure to revert to the orthorhombic phase. Both the orthorhombic and the hexagonal structures of Li.Til07 have similar scavenging capacities for Li. This paper proposes a new mechanism for the phase transformation.

Jan 1, 1991

By Yuanbo Zhang, Huanpeng Mi, Guanghui Li, Binjun Liang, Zhiwei Peng, Tao Jiang

Ludwigite ore has not yet been utilized on an industrial scale due to its complex mineralogy and fine mineral dissemination. In this study, sodium salts were employed to enhance the separation of iron and boron by reductive roasting-magnetic separation. It was found that the separation of iron and boron as well as the iron grade and recovery were significantly improved b y the addition of Na2SO4 or Na2CO3. Under the reduction temperature of 1050 °C, reduction time of 60 min and magnetic intensity of 0.1T. Compared with the inexistence of sodium salts, the iron grade and recovery of the magnetic concentrate increased from 83.3% and 88.6% to 93.2% and 95.1%, respectively, by adding 6% Na2CO3. The XRD and microstructure analyses indicated that the iron oxides were transformed into metallic iron and the average metallic iron grains were grown to over 40μm which was beneficial for separation of metallic iron from gangue.

Jan 1, 2016