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By G. Archer

ASARCO, a large and diverse producer of nonferrous metals, is involved primarily in the smelting and refining of lead and copper. Lead-antimony alloys, antimony trioxide, bismuth, cadmium oxide, selenium, tellurium, silver and gold are among products which result from processing by-products of smelting and refining. The complex mixture of concentrates at some smelters and the high impurity loads at some refineries result in various drosses, sludges, dusts and slags. In this paper, the complex interplant and intraplant transfer of by-products is addressed. These by-products result in an exchange of metals between the lead circuit and the copper circuit. Examples of the transfer of by-products and the prospects for the recycle of valuable products from wastes generated by customers and unrelated processors are also discussed.

Jan 1, 1992

By Liyuan Chai

In this study, spent grain was used as an adsorbent for the removal of Hg(II) from aqueous solutions, the process parameters such as contact time, solution pH, adsorbent dose, and initial Hg(II) concentration were studied in batch experiments. The initial adsorption process was fast, 91.08% of adsorption occurred within 5 min and equilibrium was reached at around 30min. Adsorption process was found to follow pseudo-second-order kinetics. The equilibrium data were better fitted to Langmuir isotherm than Freundlich isotherm with the maximum adsorption capacity 41.36 mg/g. The structure and component of spent grain before and after adsorption of Hg(II) were investigated using scanning electron microscope(SEM) and energy dispersive X-ray analysis(EDAX), these analysis also confirmed the adsorption of Hg(II) onto spent grain. The results indicated that spent grain had potential as a new inexpensive adsorbent for Hg(II) removal from aqueous solutions.

Jan 1, 2009

By Patricia Martínez Nicolás

Nickel and ferronickel are some of the major components in the production of special alloys; however, the energy consumption for their production greatly increases their price. A cheaper option could be to use NiO and a reducing agent. This work presents experimental and theoretical analysis to estimate the effect of slag basicity and amount of reducing agents on the NiO reduction from the slag which interacted with molten steel at 1600 °C in an EAF. The slag system contained CaO, SiO2, CaF2 and NiO together with a reducing agent, ferrosilicon or carbon. The NiO content in the slag was 25 mass%. The amounts of the reducing agents (Si and C) were 1 to 4 times the stoichiometric mass to reduce NiO. The CaO/SiO2 ratio was 1.5 and 2.5. The kinetics of the process was very fast since after few minutes the maximum nickel yield was obtained. The slag basicity had a negligible effect on the reduction of NiO.

Jan 1, 2006

By Tian Sugui

By means of the long-term aging treated, creep properties measuring and microstructure observation, an investigation has been made into the microstructure and creep behavior of the casting and rolling GH4169 superalloy after long-term aged. Results show that, after the casting and rolling GH4169 superalloy treated by long-term aged, significant amount of " phase are dispersedly precipitated within the grains of the alloy, and some of the NbC, Cr7C3 carbide are distributed along the grain boundaries. In the range of the applied stresses and temperatures, the creep activation energies and stress exponents of LTA GH4169 alloy during steady state creep are calculated to be Q=541.1kJ/mol and n=16.2, respectively. During creep, the deformation mechanism of LTA GH4169 is thought to be the twinning and dislocation slipping within the twinning regions, and the damaging mode of the alloy is the intergranular fracture, and the non-smooth crystal surface is displayed in the fracture regions of the alloy. Thereinto, the carbides film formed along the grain boundaies has a few effect on the strength between the boundaries, which is a main reason of resulting in the alloy possessing a longer creep lifetimes.

Jan 1, 2009

By K. Sanjay

Factorial optimisation technique has been used to develop regression equations at different time intervals for extraction of manganese from precipitated manganese oxide/hydroxide in sulphuric acid using charcoal as the reductant. The three parameters chosen for a 23 full factorial design were : acid concentration, amount of carbon and temperature. The regression equations were used to predict >> 90% extractions as well as kinetic data.

Jan 1, 1996

By Ryokichi Shimpo, Akio Fuwa

"The process-measurements of copper smelters in Japan were investigated for the summary of the latest technique and for the fundamental study of process control. The smelters investigated are those employing flash smelting furnace and P.S. converter, one reverberatory furnace and P.S. converter, and one continuous smelting converting furnace (M.I. process). Respective process is then considered, consisted of several reactors of different functions. The measurement methods were summarized in each reactor, including the measurement points. The methods of chemical analyses of the samples in each reactor were also investigated.IntroductionAn investigation on the process measurements, chemical analyses, and system control in copper smelters in Japan were carried out for understanding and summarizing the technique of the pyrometallurgical copper smelting operations. The typical seven processes in six copper smelters were investigated in the period from 1985 to 1987. The smelters investigated were Touyo Smelter of Sumitomo Metal Mining Co., Ltd., Kosaka Smelter of Dowa Mining Co., Ltd., Saganoseki Smelter of Nippon Mining Co., Ltd., Tamano Smelter of Hibi Kyodo Smelting Co., Ltd., Ashio Smelter of Furukawa Co., Ltd. and Naoshima Smelter of Mitsubishi Metal Co., Ltd. They include five flash smelting furnace and P.S. converter systems, one Mitsubishi continuous smelting and converting process (M.I. process), and one reverberatory furnace and P.S. converter system.The investigation was performed by making inquiries about the measurements, chemical analyses, system control, and their future prospects to the engineers in each smelter and by summarizing up in each item. The system control and future prospects were summarized in another paper titled ""Process Control Scheme of Copper Smelting Processes in Japan and Future View."

Jan 1, 1989

By L. Evrard, S. Brouwer, E. Bosly, E. Boydens

"A partial desulfurization roasting process has been tested on a typical copper-zinc sulfide concentrate in a Nichols Herreshoff monohearth pilot furnace whereby the su!fµr is partially removed and iron is to a certain degree preferentially oxidized. The phase changes that occur in the particles during selective roasting at 650°C and 800°C over a range of residence times were investigated by the use of chemical analysis, optical microscopy, X-ray diffraction and electron microprobe analyses. The purpose of this work was to get an insight into the mineral assemblages formed by controlled oxidation roasting and to evaluate if this non traditional approach could be afterwards used to recover zinc, copper and iron by a physical separation method. IntroductionThere has been considerable interest over the years in improving extraction and processing procedures for recovering non ferrous metals especially from polymetallic ores containing copper, lead, zinc and iron sulfides with very fine intergrown phases. Complex sulfide ores, which represent considerable reserves and resources in copper, lead and zinc, as well as precious metals and sulfur, are difficult to treat by conventional physical processes, leading to impure concentrates at low metal recovery. Some methods that can be used to treat such ores were described by G. Barbery (1). Various metallurgical routes generally combining pyro- and hydrometallurgical methods have been explored to develop new processes to recover the metals from zinc-bearing sulfidic ores and concentrates (2, 3, 4). The feasibility of partitioning complex sulfide minerals to simpler phases in order to improve selective extraction of mineral constituents has also been investigated (5)."

Jan 1, 1999

By Kenji Monden

A simple technique is presented to evaluate optical property of biomimetic microlens array (BMA) as an antireflective surface on a polydimethylsiloxane (PDMS) sheet. The integration of these structures is done by a thermoforming process. We have only UV-VIS spectrophotometer for optical evaluation apparatus. The transmittance of the sheet is measured with angled sample holder. The 50 deg. transmittance of 270nm pitch BMA on PDMS sheet increases from 87 to 92% after the moth-eye structure is introduced. The transmittance of 350nm pitch BMA on PDMS sheet increases from 87 to 96% after the moth-eye structure is introduced. The transmittance increases with increasing pitch of BMA. The results obtained using UV-VIS spectrophotometer with handmade sample holder.

Jan 1, 2015

By K. Murayama, M. Kawakami, T. Takenaka, S. Yokoyama

"Cokes play an important role of spacer in blast furnace. However, they degenerate during Boudouard reaction. Blast furnace cokes are reacted with pure C02 at I 072 to 1673 K. Reaction rate was obtained by the weight change of spherical specimen. The specimen after reaction was examined by microscopic observation. The reaction rate increased with temperature and was expressed by two Arrhenius type lines. The activation energy was 126 KJ/mol at higher temperature than 13 73 K and 202 KJ/mol at lower temperature range. At the higher temperature range, the reaction proceeded from the surface leaving unreacted core, whereas homogeneously whole inside at lower temperature. The porosity increased from the center to surface at higher temperature, whereas it was almost constant at lower temperature.IntroductionThe cokes have the function of fuel, reductant and spacer to keep gas and liquid flow in the blast furnace. Thus, the reaction mechanism of coke with several gas and the strength after the reaction should be important factor to control the blast furnace operation. The reaction mechanism of coke with C02 has been studied extensively. The rate equations were derived by Gadsby[ I], Ergun[2] and Turkdogan and Vinters[3]. They were compared and discussed by Kobayashi and Omori [ 4]. Effect of crystallization degree on the reaction rate was examined by Kashiwaya and Ishii[5]. Catalytic enhancement effect of ash componets have been clarified by Kashiwaya et. al. [6]. Although degradation of coke in blast furnace has been examined recently[7], however, the degradation of coke after the reaction with C02 has not been well clarified yet. In the present work, the metallurgical coke specimen was heated in N2 and C02 and the reaction mechanism and degradation behavior after the reaction was investigated."

Jan 1, 2000

By Zhiqiang Han, Anil K. Sachdev, Baicheng Liu, Guomin Han, Alan A. Luo

The growth of precipitate phase ,B-Mg11Al12 in Mg-Al alloy is closely related to interface anisotropy and elastic interaction. The aim of this work is to investigate the effects of the interface anisotropy and elastic interaction on the morphology evolution and growth kinetics of the precipitate. In the work, the precipitation of ,B was studied using phase field modeling. In the model, the chemical free energy of the precipitate and the matrix were obtained via thermodynamic calculation. It is demonstrated that the interface anisotropy results in lath-shaped precipitate and the elastic interaction affects the shape of the end of the precipitate. The interface anisotropy causes uneven growth in different directions and the elastic interaction influences its preferential growth orientation. By combining the interface anisotropy and elastic interaction in the phase field modeling, the results showed that the precipitate phase has a lath-shape with lozenge ends, which is in agreement with experimental observations.

Jan 1, 2013

By Uday B. Pal

In the electrochemical vapor deposition (EVD) process, gaseous cation precursors are passed over one side of a porous substrate, and oxygen is passed on the other side of the substrate. The gases diffuse and react within the porous substrate, and the pores get filled with the desired solid oxide. Subsequent solid state electrochemical transport through the solid oxide in the pores continues the reaction, and the film grows over the porous substrate. The EVD process has been used to deposit lanthanum chromite interconnection films and yttria stabilized zirconia electrolyte films over porous air electrodes. The EVD growth of these solid oxide films is found to be parabolic in nature, which indicates that the solid state transport (diffusion) of ions through the film controls the growth. This solid state transport can be analyzed using Wagner's treatment of the electrochemical transport. Conductivity measurements and the information on the defect structure of the oxide can be combined with the EVD growth rate measurements to calculate the solid state transport properties (transport numbers and partial conductivities) of the rate-controlling minority species in the oxide. Using this approach, the EVD growth of other electronic, mixed conducting and ionic solid oxide films can also be analyzed.

Jan 1, 1992

By H. Roberts, C. Hassall

The opening years of the new millennium will be characterised by the closure of many lead and zinc mines because of reserve depletion. However, weak commodity prices through the second half of the 1990s have slowed project evaluation and have made it difficult to raise finances for the development of new mines required to replace lost output and to meet increasing demand for metal in the future. Growth of lead and zinc demand will be determined by the pace of global economic activity, especially in the emerging economies. How rapidly demand grows will have a key bearing on the possible shortfall in mine output and the response of prices to the implied tightening of metal supplies early in the new millennium. These issues are the focus of a discussion of the critical lead and zinc supply developments which will unfold post 2000, taking into account project lead times and the role that recycled metal plays in meeting market demand.

Jan 1, 2000

By Nan Zhang, Lei Zhang, Gai-feng Xue, Lina Wang, Pu Liu

"A novel ß-diketone modified silica gel was synthesized by a simple reaction. The prepared material was characterized by diffuse reflectance FTIR spectroscopy and it was used for the adsorption of heave metal ions in the industrial waste water. The main parameters affecting the sorption of heavy metal ions, including pH, water flow rate, and elution, have been investigated in detail. Under the optimized operating conditions, most of the targeted heavy metal ions could be removed. The material could be simply regenerated by hydrochloric acid solution. The method is rapid, selective, economic and applicable to the removal of heavy metal ions from industrial waste water.IntroductionToxic organic pollutants and heavy metals ions mainly from industrial activities such as plating, metallurgy and dyeing industries, are a threat to human health and the surrounding environment, because of their toxicity and persistence after being released into the natural environment [1]. These pollutants must be removed or degraded to an acceptable level, before being discharged to the receiving waters. Therefore, detection and determination of heavy metal ions in industrial waste water is very important.Inductively coupled plasma optical emission spectrometry (ICP-OES) is the most used technique for the determination of heavy metal ions because of its capability for rapid multi-element detection over a wide concentration range and with relatively low detection limits. Compared to other techniques such as neutron activation analysis (NAA), X-ray fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS), ICP-OES has the above advantages. Some constituents in industrial waters, such as organic compounds and inorganic salts, may cause matrix effects. In order to achieve accurate and reliable results, an efficient preconcentration of heavy metal ions and their separation from the matrix are usually required."

Jan 1, 2012

By K. B. Shedd

Questions regarding possible adverse health effects from exposure to zeolites arose when the inhabitants of two villages in Turkey were found to have high incidences of mesothelioma, a disease generally identified with exposure to asbestos. No asbestos deposits are known in the area, but some fibrous zeolites have been found. Further investigations have resulted in conflicting opinions as to whether fibrous zeolites are related to the high incidence of mesothelioma in Turkey. The U.S. Department of the Interior, Bureau of Mines examined the habits of domestic zeolites by scanning and transmission electron microscopy. Only erionite and mordenite particles possessed acicular to fibrous habits. With the exception of a rarely occurring woolly erionite sample, the fibrous zeolites were not dimensionally equivalent to asbestos.

Jan 1, 1982

By Motoyasu Sato

Highly pure pig irons were produced in a multimode microwave reactor from powdered iron ores with carbon as a reducing agent in the nitrogen atmosphere. The grains in compacted powder absorb microwave energy selectively. Microwave-matter interaction creates thermal non-equilibrium state microscopically and enhances chemical reactions and the phase mixing at the grain boundaries very rapidly. The visible light spectroscopic techniques was used to monitor the progress of the reactions. Up to 650°C, the heated powders radiate the continuous spectrum of blackbody emission. The small non-equilibrium hot spots rise, move and finally burst in to brighter light emitting from all over the surface at 650°C. CN molecules and Fe (I) atoms were identified in the recorded spectrum. These bursts are similar to the ?ignition propagation? normally observed in chemical reactions. The line spectra originated from CO molecules have not been detected yet. The solid-solid reaction could be expected between the iron oxides and carbon to produce CO2 directly. A loss in the sample weight was accelerated during the excess-emission. These are the clear evidence that microwaves cause thermally non-equilibrium state and accelerate reduction process. The reduction of iron ore is completed at 1380°C and relatively very pure pig iron was produced. It should be noted that the impurity level of Mg, S, Si, P and Ti is only 5-10% of what is found in the pig irons produced by modern conventional blast furnaces in the steel industries. The necessary amount of carbon needed was 1/2 compared to conventional blast furnace to produce the unit weight of steel, if we applied renewable energy or nuclear power for the microwave excitations.

Jan 1, 2006

By Aiyuan Ma, Kun Yang, Weiheng Chen, Jinhui Peng, Shiwei Li, Feng Xie, Libo Zhang

In this thesis, a new process of recovering zinc sulfide ores was developed. The novel synthetic coordination leaching process mainly included two steps: microwave assisted phase reconstruction and compound coordination leaching. By applying various techniques, such as chemical composition analysis, X-ray diffractometry (XRD) and Raman spectroscopy, it could be concluded that sulfide phases would directly oxidized to zinc oxides under the 500 ºC microwave roasting and adding 30% Na2O2. What’s more, zinc leaching rate reached to 61.16% within 2 hours. Compared to the current technologies, this procedure had the advantage of avoiding SO2 emission, high leaching efficiency, simple process, manipulate easily, and low cost, which could be expected tremendous application potentials.

Jan 1, 2016

By Marcelo Mourao, Adolfo Pillihuaman, Alberto Nogueira, Cyro Takano

"The self-reduction is an alternative and promising process for production of pig iron because offers decisive benefits such as enhancing the reaction kinetic with decrease in fuel consumption and C02 emissions. The self-reduction mixture of iron ore fines, carbonaceous reducer and additives for slag forming components, without agglomeration, was tested in a laboratory rotary kiln. The additives for slag were defined for presenting two different estimated liquidus temperatures (1623 Kand 1773 K) to verify the effect of these temperatures on the iron-carbon nuggets coalescence process. These mixtures were tested at 1673 and 1773 Kin an experimental rotary kiln. After reduction-melting and coalescence processes the samples were disaggregated and the iron nuggets were classified by size. It was considered that nuggets larger than 7,93mm would be a good reference for coalescence index. Low liquidus temperature slag presented 37% of this larger fraction against only 13.5% for high liquidus temperature one. The low liquidus temperature slag would facilitate contact between the particles of iron-carbon in a rotary kiln, enhancing the coalescence.IntroductionThe slag composition usually depends on the reducer ash composition, the ore gangue, the binder composition and any fluxing material [l], and the mechanism of carbon transportation in slag that contains iron oxide reducible by carbon can be explained by the oxide reduction and the metal carburization. During carbon transportation, the carburized particle is transported to slag-metal interphases by the gravity effect, being assimilated by the metallic phase [2]. When the slag's iron oxide comes in contact with the solid carbon, it is immediately reduced, forming Fe particles and CO bubbles as it is shown in the figure l(a). The Fe particles are carburized by carbon particles; they are liquefied simultaneously in the carbon-slag interphase. The Fe-C liquid particles are transported from the slag-carbon interphase to iron-slag interphase as a result of slag flow, based on the surface tension difference (Marangoni effect), figure l(b). The Fe-C liquid particles coalesce on the iron surface and the carbon is immediately diffused in the iron as it is shown in figure l(c). The reduced iron is carburized continuously by repeated sequences [3]."

Jan 1, 2013

By Kumar Ganesan

Elevated mercury levels are expected in aged gold mine tailings due to residual mercury from the amalgamation process, The fate of mercury in tailings is not well understood, Its potential health risk depends mainly on the degree to which mercury is mobile in soil. Mercury is re-moved from soil by evaporation, plant uptake, microbial activities, leaching, and other physico-chemical processes. In this research the amount of mercury lost by evaporation was evaluated. Several aged gold mine tailings in Montana were sampled for total mercury and its flux into the atmosphere. Mercury levels in tailings were higher than the general background levels in most sites. The mercury levels in some cases were as high as 10,000 ug/g. The field measurements using flux chambers indicated a wide range of mercury flux from aged gold mine tailings. The mercury flux ranged from 0-11,000 ng/m2/hr. The mercury loss by evaporation helps rid the soil of mercury but the mercury vapor then will participate in the atmospheric mercury cycle, The low solubility of elemental mercury in water helps to minimize mercury leaching from tailings, however, conversion of elemental mercury to more soluble forms by bio-geo-chemical processes can enhance its mobility posing increased health risk.

Jan 1, 2003

By H. Y. Sohn

The purpose of this article is to analyze critically and quantitatively the effect of chemical equilibrium on the overall rates of fluid-solid reactions. It is shown through a mathematical analysis that a reaction with a small equilibrium constant (a positive standard free energy of reaction) is more likely to be rate-controlled by pore diffusion or mass transfer than a reaction with a large equilibrium constant. The overall reaction rate of the former also tends to be slow. Furthermore, the apparent activation energy of such a reaction approaches the standard enthalpy of reaction (M-f'), rather than the true activation energy of the chemical reaction. The Law of Additive Reaction Times developed by the author is shown to apply to equilibrium-limited fluid-solid reactions and to be useful in quantitatively analyzing the behavior of such reactions.

Jan 1, 2003

By T. Ikeda, M. Maeda, K. Mita

Galvanized steel sheet is the major product for the automobile industry. Therefore, automotive recycling results in zinc-containing scrap that should be remelted in EAFs. Naturally, the EAF dust is a very important source of zinc for zinc recycling processes. The thermodynamic properties of the Fe-Zn intermetallic compounds formed on the surface of galvanized steel sheet should be clarified to make clear the evaporation mechanism of zinc; however, there are few reports on these compounds because of difficulties in their synthesis. There are various intermetallic compounds in the Fe-Zn system. We synthesized them at about 673K. A specimen was examined chemically and X-ray diffraction was applied to ensure the formation of intermetallic compounds. Material containing two phases was placed in a Knudsen type effusion cell and the mass spectrum studied to evaluate the vapor pressure of zinc. The thermodynamic property of intermetallics was then evaluated through measured intensity.

Jan 1, 2000