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By Chuanlin Fan

The process of flotation separation and recycling of spent potlining (SPL) was described. On the basis of the laboratory investigations, the effects of influencing factors in froth flotation process, such as grain size, flotation agent dosage, pH value, pulp density, and dissolved components concentration, etc, were carefully studied. And the influence on environment of the process was also discussed. It was found that flotation separation can be used as an environment-friendly method for treatment of SPL residue. Carbon and other compounds (include cryolite, sodium fluoride, calcium fluoride and diaoyudaonite, etc.) from SPL were separated and recycled as flotation products respectively.

Jan 1, 2009

By Wilson Acchar

The accelerated growth of urbanization processes and current environmental concerns brought to light the existing enormous quantity of construction and demolition waste (C&DW). Considering the frequent lack of adequate landfill areas available for the disposal of these materials, their use in the manufacture of ceramic products has been attracting a growing interest from researchers and is becoming common practice, with the consequent relief in public administration concerns for the C&DW appropriate management. This work describes the study of clay-based products added with C&DW collected directly from the construction industry. Samples containing up to 50 wt.% C&DW were uniaxially pressed and sintered in air in an electric furnace (950-1150 °C, 1 hour). Sintered test pieces were characterized by X-ray diffraction, apparent density, open porosity and flexural strength. The results showed that up to 50 wt.% C&DW can be added to the clay material, with no degradation in the final product properties.

Jan 1, 2009

By Elisa Alonso

Recycling is generally a more sustainable alternative to landfilling. Its financial costs however, do not always justify its practice, especially in the short term. As a result, even for precious metals such as platinum, significant amounts can end up unrecovered. In considering risks of materials scarcity for firms that require platinum and platinum products, this paper examines how recycling provides additional benefits as a risk-mitigating strategy against scarcity. The experimental platform for this examination is a System Dynamics simulation model that strives to capture the dynamics of platinum market supply, demand and price. The detailed structures of supply and demand are key features of the model. Results show that since the secondary supply of platinum depends on a supply chain separate from primary extraction, recycling can diversify the risks of primary supply instabilities and reduce the impact of price fluctuations upon firms.

Jan 1, 2009

By Olga Karabelchtchikova

Keywords: Multipass grinding, Residual stress, Retained austenite, X-ray diffraction The study investigated residual stresses behaviors and their superposition effect in D2 dies for thread-rolling applications. A nested factorial experiment was applied to test hypotheses that the residual stresses profiles change due to combination of heat treatment and multipass grinding operations, and that certain patterns can be derived due to the memory relationship between pre-existing and final residual stresses distributions. The amount of the retained austenite along with residual stresses in variation with depth was measured using x-ray diffraction technique. Statistical analyses indicate that the proposed hypotheses hold. Residual stresses distributions as well as tensile peak location were found to be significantly influenced by the treatment parameters used. Unique characteristic patterns in the residual stresses profiles were observed due to multipass grinding technique across all experimental conditions. This finding suggested a plausible memory relationship between the cutting passes, and the causes of the foregoing results are further proposed and discussed.

Jan 1, 2005

By Luciano R. G. Santos

Keywords: biosorption, cadmium, copper, biomass, spent zeolite. The majority of the industrial activities produce some kind of solid wastes. In this work two industrial residues (spent zeolite and wood sawdust) were chemically modified to increase their heavy metals sorption capacities. Manilkara longifolia (a Brazilian plant known as parajú) sawdust was first treated with NaOH and modified with different citric acid concentrations (0.6-1.2 mol/L) at 120°C, for 90 min. Infrared spectroscopy confirmed the presence of carboxylate groups in the wood structure as result of their mixing. Similarly, spent zeolites were also submitted to a chemical treatment (NaOH) to remove carbon deposited during oil cracking and to recover its sorption capacity. Batch experiments carried out at ambient temperature showed that both materials present sorption capacity for copper and cadmium comparable to weak acid ion exchange resins. A maximum of 78 mg-Cd/g and 59.7 mg-Cu/g as well as 29.9 mg-Cd/g and 14.6 mg-Cu/g were observed for the sawdust and the zeolite, respectively. The results were modeled according to the Freundlich and Langmuir equilibrium isotherms and compared with results of other studies.

Jan 1, 2005

By Vijaya Thangavelu

Biological leaching of low-grade nickel laterite is based on a non-traditional leaching of oxide minerals using heterotrophic micro-organisms. The organisms solubilise metals by excreting organic acids; these acids then form complexes with heavy metals. High salinity of water supplies and soils in the vicinity of nickel laterite ore bodies is a major abiotic stress to fungi and represents a major challenge in the application of bioleaching process in-situ. Salinity exposes fungi cells to Na+ toxicity and osmotic stress. This study examined the salt tolerance development of Aspergillus foetidus based on gradual acclimatization of organism, its salt threshold and the salinity effect on its metabolism. The biological leaching of weathered saprolite ore with the resulting halotolerant organism under saline conditions was assessed. It was observed that salinity stress affected the organism?s growth and energy utilization

Jan 1, 2006

By J. C. Agarwal

Slags produced by modern smelting furnaces contain copper values which are unacceptably high for discard. The electric arc furnace is employed commercially to clean copper from flash furnace slags but the addition of highly oxidized converter slags to an electric furnace has created operational problems. Highly oxidized Noranda Reactor slags have not been processed successfully in a pyrometallurgical process. These slags, which contain large concentrations of copper (5 to 10 per cent), are treated in slag concentrators (controlled cooling, crushing and milling, and flotation) which produce a copper concentrate that must be resmelted. Though commercially operable, it will be shown that the slag concentrator has important process and cost disadvantages as compared to a pyrometallurgical process. In this paper an economic comparison is made between a pyrometallurgical process and the slag concentrator. For the analysis, five hypothetical smelting plants are considered. Each plant treats 1200 tons of copper concentrate per day and produces 109,000 tons of copper annually. The plant configurations used in this study are:

Jan 1, 1976

By Nam-Il Um

Bottom ash contains several ferrous materials (ferrous metals, Fe3O4, Fe2O3, FeS, etc.). In particular, ferrous metals contain heavy metal because Ni and Cr are chemically attracted to iron. Likewise, Cu is used to coat Ni and Cr metals as polish or to prevent corrosion. In this study, an Fe3O4-Fe2O3 double layer (similar to pure Fe) was found to have been formed in ferrous metal during air-annealing in an incinerator (1000°C). A strong thermal shock such as one that occurs during the water-cooling of bottom ash results in the breakdown of this oxidation layer, facilitating the degradation of ferrous metals and formation of corrosion products. Therefore, Fe-ion (heavy metal) oxides may be formed on ferrous metals and may be separated from bottom ash via magnetic separation. This study sought to investigate the separation ratio of heavy metals as magnetic separation and mineralogical formation of Fe-ion (heavy metal).

Jan 1, 2006

By Chen Song

Keywords: Mixed extractant, Copper, Cobalt, Nickel, Synergistic effect During separation process of copper and cobalt from nickel sulphate solution, the effects of constitutions and compositions of mixed extractant D2EHPA and PC88-A or Cyanex 272, has been studied. In one step extraction cycle, the following results are obtained:[Ni]/[Co]>4000 and [Ni]/[Cu]>40000 in nickel sulphate solution, [Co]/[Ni]>1000 and [Co]/[Cu]>30000 in cobalt chlorinate solution, [Cu]/[Ni]>10000 and [Cu]/[Co]>200 in copper sulphate solution. It was elucidated that the above-mentioned synergistic mixtures can effectively separate cobalt and copper from nickel sulphate acid solution and achieve a greater synergistic effect.

Jan 1, 2005

By Jian Yang

The mechanism of resulfurization in the desulfurization process with magnesium vapor produced in situ by aluminothermic reduction of magnesium oxide was clarified in the present work. The influences of various operating parameters on the resulfurization were studied and the methods that could prevent resulfurization were proposed. There are two kinds of mechanisms of resulfurization in the desulfurization process with magnesium. One is decomposition of the desulfurization product of MgS under the inert atmosphere. The other is oxidation of MgS under the oxidative atmosphere. Under the present experimental conditions, lowering operating temperature and oxygen partial pressure in the atmosphere could effectively prevent the resulfurization. Adding CaO onto the melt surface was an effective method for preventing the resulfurization due to transformation of the desulfurization product of MgS into the more stable compound of CaS. Since addition of the activated charcoal powders greatly decreased the transfer rate of oxygen in the atmosphere to the melt surface, it also reduced the resulfurization remarkably.

Jan 1, 2006

By Andrew Wessman

Keywords: Recycling, Electrodeposition, Recovery, Dilute, Dissolved Metal Ions In order to facilitate the recovery of pure metals from solutions containing a mixture of dissolved metal ions, a pulsed electrodeposition method was developed. Using this method, it is possible to selectively remove metal ions from solution based upon the electrochemical potential of the particular ion desired. The use of pulsed electrodeposition rather than direct current electrodeposition creates an electrodeposited material with better morphology, increases electrical efficiency of the process, and avoids problems with short circuiting between electrodes. Using this method, it is possible to recover dissolved metal ions in a purified form in one simple step, and therefore maximizes recovery of the metal ions while obtaining them in a saleable form. This method is likely to be useful in improving the recycling process for numerous complex metal mixtures and alloys.

Jan 1, 2005

By Li Zhang

Air was blown into the molten slag as oxygen resource during the dynamic oxidation. It was found that the oxidation is not only in favour of Ti components into perovskite phase, but also the increase of slag temperature and decrease of slag viscosity during the dynamic oxidation promote the precipitation and growth of perovskite phase, average crystal size of perovskite phase is 48 µm. The experimental result realizes the selective enrichment of Ti components and coarsening of perovskite phase, perovskite phase can be separated by mineral dressing method.

Jan 1, 2009

By Melissa L. Trapani

Keywords: Copper, Taphole, Flow Instability. ?Blister spitting? is a flow irregularity where the molten blister copper stream ? or part thereof ? sprays from the taphole exit rather than following a regular flow profile to the collection box. As well as being a general ?housekeeping? issue, the unpredictable nature of the flow is a threat to operator safety. Also, the aggressive flow pattern may contribute to the mechanical wear of the taphole refractory, compromising the integrity of the taphole. This paper brings together a collection of first-hand observations and reports from process personnel, and suggests some theories as to the causes of blister spitting.

Jan 1, 2005

By Jukka Tuominen

The history of making blister copper in an Outokumpu Flash Smelting Furnace dates back to the late 1960?s, when Outokumpu first piloted the Outokumpu Direct Blister (ODB) process. The first commercial scale applications have been in use at Glogow, Poland, since 1978 and at Olympic Dam, Australia, since 1988. These applications utilize special concentrates, which are low in iron, and thus the formation of slag is also low. In 1995 the same principle was applied to smelting copper matte into blister copper in industrial scale at Kennecott Utah Copper. This application, the Kennecott-Outokumpu Flash Converting process, will celebrate its 10th anniversary of commercial scale operation this year. This paper outlines the development in efficiency and flexibility of Blister Flash Smelting processes compared to other smelting and converting options. The focus is on the economical aspects i.e. on the total feasibility of both greenfield investment projects and revamping of existing smelters.

Jan 1, 2005

By Zhigang Liang

Investigation into the mixing of 150t ladle furnace by two-nozzle jetting was performed by a water model simulation of 1:4. The effects of nozzle arrangements including separation angle, radial position and asymmetry as well as tracer adding position on the mixing time were studied. The most favorable mixing is achieved when the two nozzles are symmetrically arranged at half radii in the ladle, with 45o separation angle. The empirical relationship between the mixing time and stirring power intensity has been established for two-nozzle jetting based on the present experimental results. In addition, the swelling above bath surface is also investigated with two-nozzle jetting.

Jan 1, 2009

By Xiaowen Liu

The thermal decomposition of diaspore was investigated by thermogravimetry (TG),differential scanning calorimetry (DSC), X-ray power diffraction(XRD),infrared (IR)spectrain this paper. The thermal decomposition mechanism of diaspore was discussed according to Coat-Redfer equation. It was found that the decomposition of diaspore was carried out at 500?,and the peak temperature was 530?. The electrovalent balance of diaspore was destroyed. The previous crystal structure was changed. a- Al2O3 was obtained after thermal decomposition. The activation energy is 287KJ/mol.

Jan 1, 2006

By H. Y. Sohn

The considerable progress made in the sulfide smelting technology since the first International Sulfide Symposium of 1983 is discussed. The new developments and innovations have largely been driven by the recognition of environmental concern as well as the need for increased productivity. The smelting technologies for various nonferrous metals are reviewed, with an emphasis on the industry trend towards larger plants and continuous processes. The tremendous advances made in process modeling and computer simulation to describe the complex smelting processes are also reviewed. The goal of these mathematical models is the quantitative description of the processes and the reactors that will provide a means for the control and optimization of smelting operations as well as the optimal design of the operating conditions and the reactors. Environmental issues remain a key consideration in the smelting industry. One of the most remarkable improvements made in the last fifteen years since the 1983 Sulfide Smelting Symposium is the rapid increase in the sulfur capture by nonferrous smelters. This and other related issues are briefly discussed. Finally, the challenges that the smelting industry faces as the new millenium approaches are discussed. The industry continues to face technical challenges to improve productivity and efficiency, while being responsive to ever-increasing public pressure for environmental protection. It also faces external challenges from factors that may cause the reduction of metal uses as a result of substitutions by other materials. Another serious challenge and dire consequence that the primary metals industry is expected to face is the serious diminution of university-educated manpower as well as basic-research output. To remain competitive and healthy, the industry should take up the void left by the complete disappearance, at least in the U.S., and the reduction in other nations, of the governmental support of higher education and basic research in the field of primary metals production.

Jan 1, 1998

By Javier Enrique Basurco Cayllahua

In this work, a gram-positive bacteria was used as biosorbent to elucidate the aluminum load capacity under different conditions related to metallurgical and chemical plants. The sorption data followed the Langmuir, Freundlich, Dubinin-Radushkevich isotherms. In order to determine the best isotherm fit, three error analysis methods were used to assess the data: correlation coefficient (R2), residual root mean square error (RMSE) and Chi-square test. The error analysis established that the Dubinin-Radushkevich model fits better the aluminum biosorption data. The maximum sorption capacity was found to be 41.59 mg.g-1. The maximum removal of aluminum was 95% at pH around 5. The experimental kinetics data was evaluated considering two models (pseudo-second order and pseudo-first order). This study indicated that the R. opacus is an environmental friendly biosorbent.

Jan 1, 2009

By David Arana

The use of gas-water dispersion of a molten material flow onto a vibrating surface is developed as a process to minimize water pumping requirements, minimize the risks of explosions, and minimize the post solidification dewatering and fines handling equipment requirements. The process uses existing vibration transport technologies and common plant utilities. Plant trials using the smaller footprint and the progressive molten particle cooling time have yielded encouraging results. The results are analyzed and reported.

Jan 1, 2006

By Naiyang Ma

Along with steel production, various steelmaking slags are constantly generated at considerably high rates. In general, steelmaking slags are not categorized into hazardous materials and do not cause any environmental issues. Therefore, recycling of steelmaking slags is often aimed at creating values by using the slags to replace high-cost raw materials. Chemical compositions and particle size distributions of slag products from steelmaking slags will determine what raw materials the slag products can replace. Consequently, maximizing the values of steelmaking slags will require to produce slag products with the highest values and to process the slags with the lowest costs. In this paper, several slag processing processes are assessed based on maximization of the values of the steelmaking slags.

Mar 1, 2017