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By Agnes Y. Lee

he U.S. Bureau of Mines developed a method to treat lead-contaminated soil and ebonite battery casing wastes to produce a nonhazardous material. The cleanup procedure involves wet screening to separate a minus 18-mesh soil fraction; removal of metal1ic lead, rocks, wood, etc. ; carbonation to change lead sulfate to acid-soluble lead carbonate; size reduction; acid leaching; and rinsing. The casing wastes undergo size reduction and washing to remove the lead sulfate sludge before carbonation. Similarly, the minus 18-mesh soil is carbonated, then acid leached and rinsed. In leaching, fluosilicic acid (H SiF,) and hydrogen peroxide (H20,) are used to dissolve lead compounds. An electrowinning method is employed to strip lead from the lead-rich leachate. The acid content in the leachate is replenished with fresh H,SiF, acid prior to recycling. Treated casing wastes and soils pass the Toxicity Characteristic Leaching Procedure (TCLP) test and can be reclassified as nonhazardous materia1s. Based on this process, a conceptual pilot plant has been designed which will be demonstrated on wastes from two Superfund sites.

Jan 1, 1993

By Wolfgang Koch, Bernd Friedrich, Ann-Kathrin Maurell-Lopez

Due to the high standards for silver in electronic uses, it is essential to control the behavior of the main impurities such as copper or palladium during electrolytic refining. In regard to palladium, it is indispensable to understand and manage its co-deposition behavior. The influence of electrolyte composition, current density, and acid concentration on Cu and Pd co-deposition during silver electrorefining is systematically investigated.

Mar 1, 2017

By Run-bo Wang, Zhe Wang, Fan-yi Meng, Jian-Liang Zhang

The influence of semicharcoal substitution for coke breeze on sintering performance was investigated by pot-grate sintering test. At a fixed fuel ratio, sinter productivity and strength decreased with the substitution increasing from 0 to 100% due to better combustibility. To enhance the utilization efficiency of 100% semicharcoal, sintering parameters (moisture and suction pressure) was adjusted. With the moisture increasing, sinter performance of 100% semicharcoal increased because of the suppression of semicharcoal incomplete combustion. As the moisture further increasing to 9.0%, sinter quality gave rise to a decrease trend. The results also showed that the increase of suction pressure was benefit for the increase of heat transfer rate, leading to the improvement of heat utilization energy. Measures to enhance magnetite oxidation during sintering are discussed based on current understanding of the fundamentals that control the sintering process.

Jan 1, 2015

By Yuanbo Zhang, Bingbing Liu, Zhuyin Chen, Xiao Kang, Chen Liu

Composite agglomeration process (CAP) is an effective method to utilize the iron-bearing dusts generated in the ironmaking plants, by which the dust percentage in the sinter feed can be increased up to 20 wt %. In the current study, a comparison on behavior of iron-bearing dust in the conventional sintering process (CSP) and CAP was characterized. The results showed, in the CSP products, the scattered iron-bearing dust in the mixture was disadvantageous for the sintering indexes and consolidation of the finished sinters. In the CAP products, the main phase in the iron-bearing dust pellets was well-crystallized Fe2O3 grain particles. In the matrix parts, there were more Fe3O4 particles generated, which caused to high RDI+3.15 and low RI of the finished products. The pellets and the matrix parts were bonded by iron oxides and acicular calcium ferrite.

Jan 1, 2016

By In-Hyeok Choi

Currently, spent V2O5–WO3/TiO2 catalysts contribute significant amounts of solid waste following increasing levels of global demand. V2O5–WO3/ TiO2 catalysts usually consist of TiO2 anatase as a supporting oxide, vanadium as a catalytic agent, and other promoters such as tungsten, silicon, and calcium. Although vanadium is the main catalytic agent, a relatively high content of tungsten (WO3, 7–10 wt%) typically exists compared to vanadium (0.5–1.5 wt%). Considering the irreplaceable properties and industrial importance of tungsten, a feasible method for the recycling of spent V2O5–WO3/TiO2 catalyst should be established to utilize it as a secondary source. This paper presents a process to recover tungsten from spent V2O5–WO3/TiO2 catalyst. The processes proposed here involving roasting, decomposition using HCl, ammonia leaching, and crystallization. Within the process, ammonium paratungstate (71 wt% as WO3) is obtained as a final product. The total yield rate of tungsten from feedstock was found to be 96.3%.

By Bao Xiancheng

Jinlong's copper flash smelting process started up in April 1997. In the early days of production, lots of equipment and process problems were encountered. But, through continuous improvements in equipment and operation, the designed productivity was reached two years later and the smelting operation has been greatly upgraded since then. After more than 4 yew of production, we have made great achievements, such as increasing the flash furnace availability, significant improvements in operation control, optimization of concentrate burner's structure and operation, and smooth operation of the whole smelter. This paper outlines Jinlong's operational achievements made after commissioning, and discusses problems that were encountered and their countermeasures. Operational experience is also summarized

Jan 1, 2002

By J. R. Sarazin

Density driven convection during solidification has been recognized for some time to result in macrosegregation particularly when lower density alloying elements are rejected into the interdendritic liquid. The resulting segregates are commonly referred to as channels, freckles or A-segregates. Buoyancy driven convection leading to channel formation has been examined in three model systems possessing somewhat different materials parameters. They are the Pb-Sn eutectic system, the transparent aqueous-salt NH C1-H 0 4 2 eutectic system and the transparent organic succinonitrile-ethanol monotectic system. Convection in these systems is controlled by a balance of buoyant and viscous forces, which are strong functions of composition and temperature. Composition, temperature and flow velocity were measured and elimination of channels through heavier ternary additions is discussed.

Jan 1, 1991

By James Bennett, Jinichiro Nakano, Anna Nakano

Previous empirical research demonstrated that by mixing gasification and metallurgical slags at a specific composition in a CO2 enriched environment, enough exothermic heat would be generated to transform CO2 to CO. The process capacity may be limited by the availability of the slags, however, it could be used to supplement existing energy or chemical production to reduce overall carbon emission. In this study, computational simulations were performed to explore optimal process conditions based on effects of individual slag constituents and thermal input for maximal gas conversion rate, heat production, and volume increase. In simulated conversions of CO2 to CO and H2O to H 2, comparisons were made by varying CaO, FeO, versus V2O3 slag constituents. The result indicated the optimal slag composition may be obtained by appropriate source selection and mixing of gasification and metallurgical slags in order to maximize carbon reduction and/or H2 production.

Mar 1, 2017

By Akira Kaneda, Nozomu Hasegawa

"In the Mitsubishi Continuous Copper Smelting and Converting Process, slag/matte mixture overflowed from the smelting furnace is separated continuously in an electric furnace (slag cleaning furnace, CL-furnace). In order to improve the separation efficiency of slag and matte and to minimize power consumption, the design and the operating conditions of the CL-fumace should be optimized. In the previous study, the authors developed a mathematical model for simulating phenomena in the CL-furnace. The model consisted of 3 modules, electric field analysis, heat and fluid flow analysis and the particle tracking method. In this study, the model was partially modified: k -E. model was adopted, and the effects of various conditions, such as furnace shape (including accretion) and scale, electrodes configuration, immersion depth of electrodes, and thickness of slag layer, were evaluated. And the optimum design and operating conditions were discussed.IntroductionUnder the recent environmental restriction, advantageous features of the Mitsubishi process have attracted much attention. The process uses 3 furnaces connected by launders. Mixture of matte and slag formed in a smelting furnace flows continuously to a slag cleaning furnace (CL-furnace), where the matte is separated from the slag. The matte is continuously siphoned out to a converting furnace and converted to blister copper. The slag overflowed from the CL-furnace is discarded. Because the slag contains about 0.6 % copper, improving slag/matte separation efficiency and decreasing copper loss make a great profit. Moreover the process requires a large amount of electric energy, so reduction of electric power consumption brings in enormous benefit.The objective of this study is to optimize the design and the operating conditions of the process, especially the CL-furnace. This will be achieved by developing the mathematical model and clarifying relations between the design or the operating conditions and various phenomena in the furnace. Fig. 1 shows an outline of the CL-furnace. The mixture entering through an inlet is separated to slag layer and matte layer . In order to maintain the temperature of the melt at a predetermined level, 6 electrodes are immersed into the lag and Joule's heat is generated by 3-phase alternating current flowing."

Jan 1, 2000

By K. Adham

"Fluidized beds are utilized in a wide range of high-temperature applications throughout the metals and materials industry. Their main advantage is the fast and uniform heat and mass transfer between the hot combustion gases and the particulate solid feed. A further benefit can be the lowering of the processing plant's energy consumption, through heat recovery from the fluid bed processes used for solids heating. Here, the enhanced energy efficiency of fluidized systems is investigated and the modeling results are discussed for three configurations: the flash tube, the single bubbling bed and the multi-stage fluid bed. Key thermal design aspects of each system are identified based on results from process simulations, in order to benchmark their main operating features and overall energy efficiency. Suitability and applicability of each configuration is also discussed based on a number of process and material property considerations.IntroductionCombustion based heating of particulate solids is commonly done using three different types of fluidized beds. The flash tube (FT) is similar to a hot pneumatic transport system. The single-stage fluidized bed (FB) typically uses in-bed combustion. The multi-stage fluidized bed (MSFB) can have two or more stages stacked into a tower.Flash tube (FT) suspends the incoming solid charge in a high-velocity stream of hot combustion gases. To maintain the solids suspension in the FT, two parameters are required: high velocity for elutriation of the particles and adequate solid-to-gas ratio for avoiding high pressure drops and solids drop-out [l].The fluid bed (FB) works at much lower velocities than the flash tube. Therefore, most of the solids are not conveyed in the gas stream, but are only suspended in a liquid-like manner. At minimum fluidization velocity (Umr), the gas flow exerts just enough force on the solids to keep them suspended in place [2].Multi-stage fluid bed (MSFB) heats up the solids as they are transferred from an upper bed level to a lower one, counter-current to the rising flow of hot gases generated at the lowest stage. As the temperature and volumetric flow of the gases decrease from bottom to the top stage, smaller bed diameters can be used in the energy recovery stages [3]."

Jan 1, 2014

By Satu Strömberg

Four different nickel concentrates were oxidized in a laboratory scale laminar flow furnace in simulated flash smelting conditions. The major nickel- and iron-bearing minerals in the con- centrates were pentlandite, violarite, gersdorffite, and pyrite and pyrrhotite, respectively. Thermal decomposition, ignition and oxidation behavior of nickel and iron sulfides were examined by using optical and scanning electron microscopy. General reactivity of the concentrates was monitored with sulfur removal which was most effective in violarite-based concentrate. Pentlandite-concentrates needed higher experimental temperatures for complete desulfurization and gersdorffite-based concentrate contained 5 - 10 % of the original sulfur even in the most oxidizing conditions studied (1 100°C, 50 vol-% 02). The reactivity of the iron minerals was found to depend on the other minerals present in the concentrate. In this paper, the observed re- action products and mineralogical changes are presented and preliminary conclusions of possible reaction mechanisms of nickel-bearing minerals are discussed.

Jan 1, 1997

By Heinz Boeni, Daniel Ott, Uca Silva

"Latin America is facing a rapid increase in internet use. Penetration with electronic equipment is in some countries approaching the level of industrialized countries. There is an evident need to resolve the management of “end-of-life” computers and other electronic equipment. Several studies in Latin America assessed the increasing e-waste quantities and confirmed the importance of a sustainable e-waste management. This paper gives an overview on the status on e-waste management in Latin America, explains the challenges for establishing an e-waste management system in a developing country setting and highlights the social and economic potential and the possibilities of a regional approach.IntroductionGlobal ICT-Trade and generation of e-waste from ICTThe global production of electronic devices and particularly of Information and Communication Technologies (ICT) faces the biggest industrial expansion of the history: OECD figures show that global trade of ICT technologies has reached 7.7% of the gross world product by 2004, the major proportion accruing from China [1]. In 2006 an estimated 230 million computers and 1 billion cell phones have been sold worldwide which corresponds to a volume of 5’848’000 t [2]. As a consequence, Waste from Electrical and Electronic Equipment (WEEE), or e-waste, is by far the fastest growing waste component. It reaches more than 5% referred to Municipal Solid Waste and e-waste generation in developing countries according to UNEP is expected to triple by 2010 [2].According to the OECD e-waste is “any appliance using an electric power supply that has reached its end-of-life” [3]. The European WEEE directive [4] distinguishes 10 categories of ewaste: Big household appliances, Small Household Appliances, IT and Telecommunications Equipment, Consumer Equipment, Lighting Equipment, Electrical and Electronic Tools, Toys, Leisure and Sports Equipment, Medical devices, Monitoring and Control Instruments, and Automatic dispensers. In this paper e-waste and WEEE are used as synonyms. Focus will be laid on e-waste from IT equipment (IT-waste), corresponding to category 3 of the European WEEEDirective."

Jan 1, 2008

By T. Fujita

The removal of phosphorus is essential 1n order to increase the recycling of steelmaking slags for their manganese, iron and lime contents. This study aims at establishing the phosphorus mineralogy and its distribution in steelmaking slags, the effect of slow cooling, and the methods of phosphorus removal. A series of steelmaking slag samples was prepared at different cooling rates, and the mineralogy, chemistry and grain size of the samples were investigated with SEM/EDS and x-ray diffraction. The test results using high gradient magnetic separation are discussed.

Jan 1, 1988

By L. I. Rosato

A novel hydrometallurgical process for the recovery of silver and gold from neutral leach residue that is based upon leaching with thiourea, is described. Laboratory and pilot plant studies have shown that 80-90% of the silver and 60-70% of the gold can be recovered by:? ( i) leaching zinc calcine with 'Spent electrolyte at pH 2.0-3.0 to generate a precious metal-bearing zinc ferrite residue, (ii) leaching of the thickened zinc ferrite with 3-5 g/L thiourea in a six stage carbon-in-pulp circuit, (iii) elution of silver and gold from the loaded carbon with a thiourea- butanol solution, (iv) thermal regeneration of the stripped carbon and (v) recovery of the precious metals from the pregnant eluate by cementation with zinc dust. The reasons for adopting the thiourea CIP leach and the preferred operating parameters for each process step are presented. The requirements for the destruction of any thiourea transferred to the zinc circuit are outlined, and the results of an integrated one tonne/day pilot plant operation at Canadian Electrolytic Zinc are given.

Jan 1, 1990

By José Palacios, Mario Sánchez, Fernando Parada

As an alternative method of reducing the large amount of slag generated during metallurgical processes in the primary copper production, it is to use the remaining iron in the slag as feed material for the iron and steel industry. The slag is generated during copper concentrates smelting in ratios ranging from 2 to 5 ton per ton of produced copper, and it contains 42–45% of iron. However, copper, sulfur and other detrimental elements affecting iron properties need to be reduced prior to use the slag in steel production. Therefore, some laboratory experimental run has been conducted to reduce copper by slag oxidation followed by leaching and recovering the dissolved copper by SX-EW, and smelting the solid with coke to produce a metallic phase containing 98% iron and 0.9% molybdenum. In further reducing steps, copper content is lower down and a molybdenum rich iron phase is obtained. Recovery of iron from copper slags considering reduction and control of harmful elements for iron properties was studied.

Mar 1, 2017

By I. M. Richardson, M. Janssen, W. Geerstma, I. J. Bennett, V. A. Popovich

Avoiding wafer breakage is a big challenge in the photovoltaic silicon industry, limiting production yield and further price reduction. Special fracture strength tests suitable for thin silicon solar wafers and solar cells, to be used in combination with Weibull statistics, finiteelement (FE) modelling and digital image correlation have been developed in order to study the mechanical stability of solar wafers. The results show that removal of the saw damage significantly increases the strength of crystalline silicon wafers. Furthermore, it was found that silicon crystallinity and the location where the wafer is extracted from the cast Si ingot have a significant effect on the strength, namely samples taken from the bottom of the ingot are 30% stronger than those taken from the top. The study also showed that there is a decrease in fracture strength when an anti-reflective SiNx coating is applied, which is caused by high thermal stresses.

Jan 1, 2015

By Pengfu Tan

NiModel, a thermodynamic model, database and computer program, has been developed to predict the distribution behavior of Ni, Cu, Co, Fe, S, O, As, Sb and Bi, and heat balance in the nickel pyrometallurgical processes such as Outokumpu flash smelting, Outokumpu direct high-grade matte smelting, INCO flash smelting, and Peirce-Smith converting processes. In this model, as much as 16 elements (Ni, Cu, Co, Fe, As, Sb, Bi, S, O, Al, Ca, Mg, Si, N, C and H) are considered. The compositions of matte, slag and gaseous phases, and heat balance are calculated using the thermodynamic data and the activity coefficients of the components derived from the experimental data. The model predictions were compared with the known industrial data from Kalgoorlie Nickel Smelter in Australia, Outokumpu Harjavalta Nickel Smelter in Finland and INCO Metals Company in Canada, and an excellent agreement was obtained. In this paper, the applications of NiModel in the nickel pyrometallurgical industries have been presented. NiModel has been used by Jinchuan Group Limited in China.

Jan 1, 2004

By Robert Vidal

The performance of a laboratory-scale cell for the electrolysis of an aqueous chrome alum solution was studied. Electrode potentials, pH, and Eh were recorded. An optimum catholyte pH of about 2.5, consistent with information from the literature was observed. Values exceeding this range resulted in a precipitate formation and are detected by wavering cathode potentials. The role of anodically produced dichromate ions was investigated by chemical analysis. It was found that the steady state concentration of dichromate ions varies inversely with fluid flow from catholyte to anolyte. This concentration was also reduced with the use of precious metal coated titanium anodes.

Jan 1, 1994

By Gervais Soucy, François Quesnel, Pierre Hovington, Wen Zhu, Karim Zaghib, Jocelyn Veilleux

The properties of lithium titanates anodes in Li-ion batteries are highly dependent on their secondary constituents. While their main phase is usually constituted of Li4Ti5O12, significant quantity of lithium titanates compounds of various stoichiometry are often present, due to either the processing, usage or aging of the material. These may go underreported, as many of these spectrums overlap or display low signal in X-ray diffraction (XRD). Samples of nanosized lithium titanates synthetized by inductive plasma were characterized by XRD and scanning electron microscopy (SEM), as they provide a regular yet typical crystallite size and shape including multiple phases. A Rietveld refinement was developed to extract the composition of these samples. Mass balance through further annealing and differential scanning calorimetry (DSC) enthalpy measurements from phase transformations were also used as identification and validation techniques.

Jan 1, 2015

By Djalma Souza, Jean Igor Margem, Sergio N. Monteiro, Frederico M. Margem

Synthetic fibers have been used for many years to attend the demands required by the technologica lfields. However, the use of them has been questioned due to the impact on the environment. In this way, the natural fibers have received extensive attention, in particular hybrid fabrics of natural fibers to reinforce environmentally friendly polymer matrix composites. Thus, the present work has the objective of evaluating and comparing the mechanical properties of composites formed by hybrid fabric with 70% Malva—30% Jute in epoxy polymer matrix. The tests carried out are the Charpy and Izod Impact Tests, with specimens of 10, 20 and 30% in volume of hybrid fabric environmentally friendly into polymer matrix composites at room temperature. The 30% samples had the best results, functioning as an efficient reinforcement.

Mar 1, 2018