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By John W. Graydon

Incineration is an attractive alternative to the disposal of MSW in landfill sites. However, the process of incineration generates fly ash which contains significant levels of leachable heavy metals - particularly cadmium, lead, and zinc - and it is essential to manage this fly ash in an environmentally sound manner. The compositions, phases, textures, morphologies and size of fly ash particles have been studied by light microscopy, scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. The detailed spatial relationships and speciation of the environmentally significant constituents have received particular emphasis. The information obtained is useful in understanding how fly ash is formed during incineration, in understanding the leaching behavior of untreated fly ash if it is disposed of in a landfill and, most importantly, in guiding the development of the best treatment strategies for fly asti to mitigate its environmental impact.

Jan 1, 1992

By Larry M. Southwick

There is much ongoing work in research and development of new processes for the recovery and recycling of met.a.ls and other materials from various waste and scrap streams. Commercialization of such new technologies requires the bringing together and successful execution of a considerable effort involving a variety of activities. These include process conceptualization, research and development, detailed design and construction, and then plant startup and operation. Processes evolve through all of these steps by engineering due diligence, making objective and critical analyses of results, and troubleshooting processing steps to, hopefully, arrive at a sequence that has the best chance to succeed operationally and economically. After a summary review of the above steps, several processes will be described in more detail that provide mostly successful examples of the above procedures. Finally, some observations will be made on areas that will become critical in the near future to the success of new processes for wastes and residues.

Jan 1, 2000

By J. Murdoch Mackenzie

Two commercial nickel solvent extraction plants treating laterite leach solutions and using LIX®84-I have been operated in Australia. These circuits employ similar extraction chemistry but differ in their leaching and stripping operations. An alternative process involving elements of both can be conceived. The preparation of the feed solution to solvent extraction plays an important role in nickel extraction using LIX®84-I and the special features of manganese removal and cobalt oxidation in the preparation of the PLS are discussed. This paper compares these three circuit configurations with special reference to the extraction and reductive stripping of cobalt, the transfer of zinc and copper to the strip aqueous, ammonia transfer and sulfur transfer. The potential degradation of the organic and remediation using re-oximation is discussed. Keywords: Nickel, Solvent Extraction, Oxime

Jan 1, 2004

By Chris Doyle

From 1997-2000. PT INCO undertook the Fourth Line Expansion Project (FLEX) to increase annual production rates from 90-100 to 150 Mlbs Ni/year (68,000 MT Ni/yr). In 2003, PT INCO nickel production underwent a major sustainable step jump that finally exceeded the targeted rate. This paper presents the changes that led to this achievement. The focus of mining changed. Improving Ni grade was important but only if electric furnace feed met target chemistry so that on-specification slag could be produced. The intensity of diamond core drilling for exploration was dramatically upgraded, mine planning strategy was totally re- vamped and an ore chemistry quality assurance team was formed. In the processing plant, measurement systems were upgraded for better control. Teamwork between sections vastly improved. The final step jump in production occurred when the fifth hydro-electric power generator was added to the furnace grid to allow the power-starved furnaces to cruise in operation at 70+ MW. Keywords: Free cash flow, Ore Chemistry, Measure, Control, Improve

Jan 1, 2004

By J. A. Holmes

Due to varying and complex mineralogy, the flotation tailings from the Chingola Concentrator have, for some years, contained upwards of 0.4% acid soluble copper. In 1968, an investigation was initiated, to determine a method for recovering this acid soluble copper. This initial investigation concluded with a recommendation to install a leach-solvent extraction-electrowinning plant at Chingola, to treat up to 900 000 tonnes of material per month, for an additional copper production of some 4 500 tonnes per month. The process consists basically of six stages :- Materials reclamation handling and preparation, acid leaching in air agitated pachucas, solid-liquid separation by countercurrent washing in thickeners, solution concentration and purification by solvent extraction, copper recovery by electrowinning, and residue neutralisation and disposal. This paper describes the development of the main parameters for design of each of the six sections, and gives details of the final plant design. Problems encountered in commissioning and initial operations are commented on, particularly insofar as they indicated any errors or misjudgements in the design. The choice of materials of construction is commented on in some detail.

Jan 1, 1976

By Lloyd R. Nelson

Experimental results of three-phase mixing in a physical model of a CCRL for metals refining are presented. The system was operated above a critical lower liquid height-to- width ratio (H,/W) of unity, with adequate bottom gas injection through a line of central, single tuyeres (Q,/A = 7.5 cm/min, or c = 17 W/m3) to sustain levels of interphase transport considered appropriate to an industrial pyrometallurgical refining operation. The application of a thermal tracer technique to elucidate both longitudinal mixing and interphase heat transfer is discussed. The results indicate that even under conditions of significant bottom gas injection, it should be possible to maintain acceptably low longitudinal mixing 1 (D, < 20 cm /s and D,/uL < 0.1) in the CCRL. Interphase mass transfer coefficients of the order of 0.004 cm/s are predicted from the measured interphase heat transfer coefficients (h = 1.3 to 2.0 kW/m2K), using the heat and mass transfer analogy. Adequate rates of rehning are predicted for an industrial CCRL operated under such conditions.

Jan 1, 1995

By Hong Liang-shi

Olivine lithium iron phosphate (LiFePO4) is considered as one of the most promising materials for lithium-ion secondary batteries because of its high theoretical capacity, low cost, good safety, benign environment and good cycle performance. In this paper, carbon-free and/or carbon-coated olivine lithium iron phosphate composite ultrafine powders were successfully synthesized from aqueous precursor solutions of (NH4)2Fe(SO4)2?6H2O, H3PO4 and LiOH?H2O by co-precipitation method. The obtained LiFePO4 or LiFePO4/C powders were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Their electrochemical performance was investigated in terms of cycling behavior. As confirmed by X-ray diffraction and scanning electron microscope, the material obtained by co-precipitation within the temperature range of 60ºC to 100ºC and then followed by moderate heat treatment are a single-phase olivine LiFePO4with the particle size of about 300nm. An improved carbon-coated olivine LiFePO4/C material was prepared by adding conductive carbon materials, such as glucose, activated carbon and acetylene black, into the precursor. The carbon dispersed in the materials increases the electronic conductivity of LiFePO4/C composite, and consequently, leads to high rechargeable capacity of the material. The carbon-coated material with carbon amount of 7.64%wt obtained from glucose has the first discharge capacity of 150.3mAh/g at the rate of 0.1C and 129.3mAh/g at the rate of 1.0C, respectively. After cycled for 50 times, the capacity retention rate is 95.13% at the rate of 1.0C in the voltage range of 2.5 to 4.3 V vs. Li/Li+.

Jan 1, 2006

By Bowen Li

Copper vermiculite is a special nanomaterial with excellent antibacterial and antifungal performance. By means of ion exchange, copper vermiculite containing up to 5.8wt% copper was prepared. The chemical and mineralogical characterization of the material was investigated in this study based on the XRD, AAS, TEM and EDS analysis, as well as the calculation of crystalline parameters and crystal chemical formula. Cu2+ and Mg2+ have similar atom radius and same electrovalence. Correspondingly, the structure character of copper vermiculite is very close to that of standard Mg-vermiculite. Most of the CU21 may have occupied the interlayer cationic positions in the form of hydrate in vermiculite. However, some may have entered into octahedral coordinate positions. The values of au and bo of the copper vermiculite crystal cell have no obvious change compared to that of original vermiculite micropowder, but the Co value decreased slightly, which is desirable for the stabilization of the Cu2+ in copper vermiculite.

Jan 1, 2003

By Paul L. Wichlacz

A mathematical model of growth and ferrous iron oxidation for attached bacteria was applied to rotating biological contactor (RBC) units treating acidic mine drainage. The model describes attached bacterial growth as a saturation function, where the rate of substrate utilization is determined by a maximum substrate oxidation rate constant, a half saturation constant, and the concentration of substrate within the RBC. The maximum oxidation rate constant was proportional to flow rate and the substrate concentration in the reactor varied with influent substrate concentration. The model was tested at three separate sites and with three different size RBC units. The ability of the model to predict the rate of iron oxidation under all test conditions was significant. The accuracy of the model was found to be affected by unit size and vary with specific test site.

Jan 1, 1985

By Cesimiro Fabian

The crystallite size of copper electrodeposits was determined by X-Ray powder diffraction analysis using a General Area Detector Diffraction Solution (GADDS) diffractometer. Crystallite size was calculated for copper thin films which were deposited on a 316 stainless steel rotating cylinder electrode (RCE) in the presence and absence of additive ?A?. The crystallite size was calculated from a corrected full width at half maximum (FWHM) of the [110] peak profile using the Scherrer equation. The test of significant difference on crystallite size was derived using Kruskal-Wallis method. It was found that in the absence of the additive the median crystallite size was 426, which decreased to 364 in the presence of the additive. As the additive degraded, the crystallite size increased to a size similar to that observed in the absence of additive.

Jan 1, 2003

By I. Mc Dougall

"The matte/slag tidal zone in a platinum smelting furnace is subject to severe process conditions which can often lead to premature failure of the lining. The MgO-FeO-Si02 slag is aggressive to refractory bricks, whilst the Ni-Cu-Fe-S matte is aggressive to water-cooled copper cooling elements, and can penetrate and sulphidize refractory bricks, particularly at the high matte temperatures often experienced in the PGM industry. A novel approach to the lining design was taken at Lonmin's new 10MW Furnace 2. An indirectly-cooled graphite ring was applied in the matte/slag tidal zone, with refractory bricks on the hot face. Thermal Finite Element modeling was conducted to determine the optimal lining design in this region of the furnace. The resistance of two graphite grades to damage by slag and matte was evaluated experimentally. The graphite lining is not wet by the matte, and is resistant to slag attack at operating temperatures. In comparison to water-cooled copper in various configurations, cooled graphite shows promise as an indirect refractory cooling system in the tidal zone area of furnaces.IntroductionIn South African Platinum Group Metals (PGM) smelting operations, the PGMs are associated with nickel-copper sulphides in magmatic rocks. After ore is mined, it is concentrated by means of a flotation process prior to smelting. Both rectangular 6-in-line and circular 3 electrode AC submerged arc furnaces are used for this purpose. A new 10 MW round furnace is currently under construction by Tenova Pyromet at Lonmin's Marikana Smelter Division. An overview of Lonmin's smelting operations and Lonmin's approach to smelting high chromite containing PGM concentrates is given by Eksteen et al. [1]"

Jan 1, 2012

By Marco Pasetto

The possibility to re-use marginal materials (by-products) deriving from industrial activities in the construction of road infrastructures, as total or partial substitution of natural aggregates, successfully combines demands for economy and environmental sustainability. The paper presents the results of a laboratory study, conducted at the Experimental Road Laboratory of the University of Padova, to verify the suitability of a particular type of electric arc furnace slag to be recycled in the lithic skeleton of high-performance asphalt mixes (porous asphalt, high modulus mixes, stone mastic asphalt, nonskid surfacings) for road and airport flexible pavements. the process of transformation of iron and steel slag into a product that can be used in road building is described, along with the characterisation of the mixtures, plus an analysis of the results of a wide battery of mechanical-performance tests. This study forms part of wider theoretical ? experimental research being done at the University of Padova in order to improve knowledge of the characteristics of succedaneum materials and check their possible applications in road and airport construction.

Jan 1, 2006

By S. G. Galbraith

We have used the principles of supramolecular chemistry to develop reagents to transport metal salts. These reagents have separated charged "compartments" which recognize a metal cation and its attendant anion(s). They are easy to manufacture as they are structurally related to the commercial hydroxy-oxime extractants for copper. Efficient protocols for loading and stripping of these extractants depend on the novel feature that they bind the metal salt in a zwitterionic form of the ligand. Transfer of the phenolic protons to the pendant amines generates the charged "compartments" to accommodate the metal cation and its attendant anion(s). This paper focuses on how these types of reagent can be used to recover base metals from sulfate and chloride media in flowsheets in which solvent extraction effects separation and concentration operations, interfacing between conventional leach and electrowin/reduction processes. Work on the development of reagents that have high selectivity for metal chloride/sulfate transport, convenient stripping protocols and appropriate hydrolytic stability will be described.

Jan 1, 2003

By Onuralp Yücel, Mehmet Bugdayc, Murat Alkan

"In this study, iron based alloys (Fe-Mo, Fe-Cr-Ni, etc.) were produced by using aluminothermic methods starting from Mill Scales obtained continuous casting processes. Mill scales are an oxidised layer of steel alloys containing iron oxide, which includes + 2, + 3 values, on the surface of slabs and billets occurring during annealing in heating furnace at integrated iron and steel milling plant, and continuous casting unit. In the metallothermic experiments, different ratios of starting mixtures and addition of the oxide powders (Alz03, Si02, CaO, MgO) were examined, and their effects on the metal recovery and alloy compositions were carried out. The samples were characterized by using chemical analysis (AAS), XRD, XRF and SEM/EDS techniques.IntroductionSelf Propagating High Temperature Synthesis process (SHS) has many favour compared to the furnace applications, such as low energy requirement, low cost, very short processing time and simple operation, [l, 2]. In a SHS process, the ignition starts the combustion and propagates throughout the reactant mixture yielding the desired product. However, the disadvantages of the process such as inhomogeneous or unreacted products due to undesirable reaction rates needs to be overcome by changing some parameters such as ignition temperature, particle size, additive, atmosphere etc. [3, 4]. Mill scale is a layer of iron oxide which forms on ferrous materials cooling after being processed in hot rolling or continuous casting plants. Mill scale contains iron (II) and iron (III) oxides, which result in a 70% total iron content in oxide form. Not being able to reuse this material will prevent the raw material entering the production plant from being fully utilized [5]. This study aimed to produce Fe-based alloys via SHS (Self Propagating High Temperature Synthesis) metallurgy which is attractive process technique regarding fast and low-cost production ability of cast alloys by using high metallic iron content by reducing continuous casting mill scale."

Jan 1, 2013

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Peter G. Mason

Over the last 15 years numerous Pressure Oxidation and Pressure Leach plants have been installed throughout the world. The technology is no longer regarded with awe and trepidation as plants designed to treat a wide range of feedstocks continue to be successfully brought on line. Important aspects of the design of such plants include feed preparation, slurry pumping, heating and heat recovery, pressure control and let-down, vessel design, safety and provision of associated services.

Jan 1, 1999

By Isabel Lázaro

A detailed study has been undertaken into the electrochemistry of the leaching of chalcopyrite in acidic solutions containing ferric ions. Mixed potential measurements have shown that the maximum potential achievable on a chalcopyrite disk in a ferric sulfate medium lies within the so-called passive or prewave region in the anodic behavior of chalcopyrite. The very low current densities due to the anodic oxidation of chalcopyrite at potentials in the region of the mixed potential has made studies of the initial stages of dissolution difficult. However a careful rotating ring-disk electrode (RRDE) study has enabled data to be obtained for the stoichiometry of the initial dissolution reaction to be obtained. Thus, in addition to the detection of soluble iron and copper as products in this potential region, a soluble sulfur species has also been detected. A comparison of the experimental with the expected collection efficiencies of the products on the ring has revealed that this soluble sulfur species is likely to be thiosulfate. The characteristic transient anodic behaviour of chalcopyrite in this potential region has been interpreted in terms of a rate limiting solid-state diffusion process. Thus, extrapolated rates based on reported measured solid-state diffusion coefficients for the mineral at elevated temperatures have been shown to be consistent with the potentiostatic current-time transients. Furthermore, comparative studies of the anodic characteristics of the copper sulfide minerals covellite and bornite has confirmed their greater reactivity in this potential region. The results of this investigation have been combined with a parallel study of the non-oxidative behaviour of chalcopyrite in order to derive a model for the dissolution process which is consistent with other published studies of the electrochemistry and dissolution of the mineral.

Jan 1, 2003

By Roger C. Urquhart

Copper-nickel-sulphide ores mined in the Rustenburg district of South Africa are generally smelted in electric furnaces because of the high-temperature slag produced, the availability of cheap electric power, and the smaller pollution problems. Apart from melting, the functions of the electric furnace are to recover most of the matte content in the converter slag by physical and chemical interaction with the furnace bath and to provide adequate time for the optimum separation of matte and slag. Smooth, efficient operation will denend on fluid slags for settling, balanced by high resistivities to obtain adequate concentration and distribution of power by way of current heating. To obtain a greater understanding of the processes involved, an investigation was undertaken at Rustenburg Platinum Mines on the smelting of copper-nickel concentrates in a 19.5 MVA furnace with six in-line electrodes. The matte- and slag-tapping temperatures, slag temperatures, slag analyses, electrical data, and electrode position were measured. Radioactive tracers were introduced into the slag, and quantitative results relating to the flow pattern within the furnace were obtained. These studies were augmented by scaled laboratory investigations relating to the determination of cell constants and current distribution within the furnace. Instantaneous field and power distribution plots were determined by use of an on-line mini-computer. The applicability of these results to furnace operation is discussed.

Jan 1, 1976

By C. Palacios

The Plant, which was started up in April 1970, was originally designed for a capacity of 40.000 ton of cathodes per annum, using 12 sections, containing 408 cells. Since then the addition of another 8 sections containing 280 cells and using the Reverse Current System has made possible the increased output of 109.000 ton. The quality of the cathodes produced is excellent. The extension of the Electrolytic Refinery, by the introduction of the Reverse Current System, has been a great success and no problem has arisen in the new equipment or in the modifications carried out in the plant. The operation of the plant has improved due to better control procedures.

Jan 1, 1976

By Hector M. Henao

The FeOX-CaO-SiO2 base slag at intermediate oxygen partial pressures is very often used in non-ferrous smelting processes. This slag would also contain Al2O3 and MgO because these compounds are normal components in the ore and the refractory of a furnace. The objective of the present work is to determine the effect of Al2O3 or MgO addition on the liquidus temperatures of the plain FeOX-CaO-SiO2 slags in the atmosphere between intermediate pO2 of 10-6 and that of iron saturation at 1250 and 1300 °C. The experiments were carried out at given mass%CaO/(mass%CaO+mass%SiO2) ratios ranging from 0 to 1 and at spinel-tridimite double saturation. The experimental results show that the effect of Al2O3 or MgO addition on the plain FeOX-SiO2-CaO slag is not uniform and depends on the content of Al2O3 or MgO, the oxygen partial pressure and the mass% CaO/mass% SiO2 ratio. It is apparent that Al2O3 or MgO addition enlarges the spinel or wustite saturation area at almost all the oxygen partial pressures and temperatures of this research. The obtained phase diagrams will be useful in the metallurgical industry to assist in the selection of slag chemistry, operation condition and development of new processes.

Jan 1, 2006