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By Alexander V. Suvorin, Vladyslav M. Sokolov

"The traditional technologies for production of the coprecipitated and deposited catalysts are analyzed from the standpoint of diversion of application of the feedstock and increase of efficiency for its usage. The options for return of the metals of spent catalysts to the catalysts production are described. The novel environmentally friendly and cost efficient approach for reutilization of the spent catalysts is realized in practice. It anticipates application along with spent catalysts of the waste generated in the catalytic productions. Reutilization of the Ni-containing catalysts is referred as an illustration. Introduction The recent development of large catalytic manufacturing for organic and inorganic synthesis, and petroleum refinery as well as for applied environmental catalysis has brought about increase and diversification of catalysts production. The generation of spent catalysts has been increased correspondently. The feedstock for production of catalysts is mostly metals in a form of nitrates, carbonates, hydroxides, hydroxydcarbonates. Sometimes salts of organic acids, of ammoniates, of chlorides and of sulphates occur. All these materials are scarce and expensive. So their repeated use by reutilization of spent catalysts is very actual issue. The traditional recycling the Fe-, Cr-, Ni-, Cu- or Zn-containing spent catalysts are carried out by pyrometallurgical reclamation of pure metals or alloys. They can not be used directly in production of catalysts [1, 2]. The hydrometallurgical approach is used for recycling spent catalysts with PGM, W, Mo, Co, Ni or Cu. It provides production of salts of these metals in a form of sulphates, chlorides, carbonates, hydroxydcarbonates and sometimes nitrates or ammoniates. Only a limited number of these salts can be used directly in production of catalysts. Material losses during catalysts production The basic feedstock for manufacturing coprecipitated and deposited catalysts that may be produced from the spent catalysts is aqueous solutions of metals nitrates. Their production is based on application of nitric acid as a dissolvent. About half of it is lost with the flue gases in a form of nitrates vapor and nitrogen oxides (II, IV). The last compound is generated by reaction:"

Jan 1, 2008

By Wenjie Zhu

Hexavalent chromium is a widespread environmental contaminant. An Achromobacter sp. strain nominated Ch1 can reduce soluble and toxic chromate to insoluble and non toxic Cr(III) in aerobic cultures, and no Cr(VI) decrease was observed in anaerobic cultures. In contrast with other Cr(VI) reducing microorganisms, Ch1 showed higher Cr(VI) reduction at high pH. Reduction performed under alkaline conditions at pH 7 to 11, and the optimal pH was 10. During the reduction, pH decrease was observed may caused by production of acidic metabolic byproducts from aerobic respiration. In the present study, the ability of Achromobacter sp. Ch1 to reduce Cr(VI) during growth was evaluated with lactate as an electron donor. In NB medium, Ch1 reduced 100% of 24mM of Cr(VI) in 35h, but only 73% of 30mM of Cr(VI) after 48h of inoculation. Reduction was inhibited by metal ions like Ag+, Cu2+, Zn2+, slightly inhibited by Mn2+, and not affected by Mg2+. Results revealed that reduction rate of Cr(VI) also increased with the increasing of concentrations of lactate, and complete reduction was achieved at the concentrations above 40 mM. HPLC analysis demonstrated Cr(VI) reduction was associated with the consumption of lactate. There was a large quantity of dark blue sediment generated in the culture during Cr(VI) reduction by Ch1. Energy dispersive X-ray (EDX) analysis showed that the major element composed the formed sediment was chromium presented as Cr(OH)3 precipitate. The features characterizing Cr(VI) reduction by Achromobacter sp. Ch1 are high Cr(VI) concentrations and high pH.

Jan 1, 2006

By J. H. Meza

La Caridad copper smelter is located in the magnificent but rugged Sierra Madre Mountains. This project presents unusual challenges that require the utmost in detailed analysis and planning. The smelter, owned by Mexicana de Cobre, S.A. de C.V., has an annual production capacity of 225,000 metric tons of copper and 600,000 metric tons of sulfuric acid. It utilizes only the Flash Smelting process. This project will expand the annual production capacity to 270,000 metric tons of copper and 1,000,000 metric tons of sulfuric acid. Offgases from the Flash Furnace and the Teniente Converter will be sent to a mixing chamber, from which it will be led to two sulfuric acid plants. This project will then produce a high quality sulfuric acid.

Jan 1, 1995

By Hongmin Zhu, Guihua Wang, Xiangsheng Wang

"The anode process of carbon electrode in fluoride melt was studied by voltammetry and chronoamperometry. Anode gases were analyzed by gas chromatography on-line during controlled-potential electrolysis. Two peaks were observed on the cyclic voltammograms. According to the results of gas chromatography, the first peak was corresponded to the discharge of residual oxide ions, with the formation of CO and CO2. Discharge of fluoride ions occurred at 4.1 V vs. Li+/Li, and leading to the anode effect. With the occurrence of anode effect, small amount of CF4 was detected. As the potential reached 4.5 V, CF4 and C2F6 gas evolution occurred, and the current increased to form the second peak.1.IntroductionIn the primary production of Aluminum and some rare earth metals like neodymium, a departure from normal cell operation known as anode effect results in the generation of perfluorocarbons (PFCs), which have high global warming potentials [1]. Owing to the pressure of environmental protection, considerable research has been carried out to clarify the mechanism of anode effect and PFC generation of industry and laboratory cells in the aluminum electrolysis system [2-9]. The common result on PFC generation is that the PFCs are emitted from Hall-Heroult cells only when they are on anode effect. In this article, we selected LiF, the main electrolyte for the neodymium electrolysis [10-11], to perform further investigation on the underlying kinetics of PFC generation and the nature of the reactions at the electrode.2. ExperimentalAll experiments were carried out in an alumina tube reactor, which was filled with high purity helium atmosphere. Spectrographic graphite crucibles were used, which played the dual role of molten fluoride container and the counter electrode. Lithium fluoride was analytical grade. The experiments were carried out at 900 °C."

Jan 1, 2011

By Suk J. Im, I. S. Min, Daesoo Kim

UFP are defined by atoms or their clusters having diameter in the range of l0Å-0.l.um. Due to a ratio of very large surface area to volume, they have peculiar properties such as extra high surface energy. Recently UFP deposition technique may find its new applications to various areas such as conductive/resistive film formation. In this method, gas flow with UFP jet through the nozzle which is considered to be a free molecular flow is maintained at a very high speed (~100m/s). Using this technique, mixture film of Fe and Ni, and Ag/ Ag-Alloy etc. were obtained, and their mechanical and electro-magnetic properties were determined. The experimental results are pending. The test results and discussion will be presented in the main paper.

Jan 1, 1988

By I. Kim, J. C. Choi, W. D. Cho

"The effect of yttrium addition on the oxidation behavior of Fe3Al intermetallic compound was investigated in the range of temperature 800 to 1100 °C in 0.2 atm 02 in terms of oxidation rate and oxide adhesion. The oxidation rate of alloys, Fe-14.3 wt% Al and Fe-14.1 wt% Al-0.3 wt% Y, was nearly identical and the parabolic rate constant calculated as a function of temperature is Kp=5128 exp[-39506(cal/mol)/RT] mg2/cm4 hr.Rapid cooling and ultrasonic stress tests were carried out to test adhesion of scale formed on the alloys. While the oxide layer formed on the Fe-Al alloy without Y was found to be fragile and detached easily during the tests, the oxide layer formed on the Fe-Al alloy containing Y was protective, dense, and adhesive. The following two mechanisms were proposed to explain the adhesion improvement of Ah03 formed on the Fe3Al containing yttrium : (1) the addition of yttrium decrease generation of growth stress in alumina scale because the preferential diffusion of yttrium through grain boundary in alumina scale prevent internal oxidation of Al, one of main causes of growth stress, and (2) the second phase formed on the oxide scales prevents crack propagation through the scales, leading to better mechanical stability of the oxide scales.IntroductionIron aluminides have attracted the attention of many researchers as a candidate for use at high temperature because of their excellent oxidation resistance due to the formation of protective alumina scale. In order to resist aggressive environments at elevated temperatures, oxide scale formed on iron-uluminum alloy must satisfy the following three requirements : (1) thermodynamic stability (2) slow growth rate (3) adherence on substrate. According to Wallwork and Hed [l], the most suitable alloys for high temperature application are Fe, Ni, and Co alloys with the protection of Si02, Cr203, and Ah03 scales. While chromium oxide can vaporize as Cr03 above 1000 °C and silicon oxide may form low melting silicate [2,3], Alz03 has a high melting point and is the most stable among the three oxides thermodynamically [6]. In this respect, iron aluminides forming alumina seem to be most suitable for use at high temperature. However, alumina scale formed on the iron aluminum alloys tends to be easily spalled during oxidation due to the combination of growth stress and thermal stress."

Jan 1, 1998

By T. Watanabe, T. Fujiwara, S-Wan Song, Y. Nakagawa, R. Teranishi, M. Yoshimura

"We have tried a new method to fabricate cobalt oxide films onto porous films directly by an electrodeposition method at low temperature. The porous substrate films (membrane-filters and paper) were placed between a LiOH solution and a CoSO4 solution and treated under electricalcurrents of ~1 mA/cm2 using carbon cathode and anode. Effects of temperatures, flow rates and electrical currents have been investigated. As a result, we found that the LiCoO2 films and Co3O4 films were successfully fabricated on paper and/or porous PTFE filters at 120 °C, while CoOOH films were deposited at 80 °C. Furthermore, LiCoO2 films did not cover whole the substrates, but was fabricated just over the anode. The chemical reactions of electrodeposition were also considered from these results.IntroductionRecent agreements on global environment require rapid progress of low energy and low waste processings for the fabrication of thin films that succeed to the mass production with the high consumption of the fossil fuels (such as physical vapor deposition°, chemical vapor deposition2), dip coating with firing3) etc.). The total energy consumption in aqueous systems should be the lowest among all these processing routes, because a much lager excess of energy is necessary to create melts, vapor, gas, or plasma than to form an aqueous solution at the same temperature4)The ""Soft Solution-Process"" (SSP) was one of the best concepts to realize the low energy and low waste fabrication of inorganic materials. 5) Generally speaking, SSP gives similar results to any other processing using fluids (such as vapor, gas plasma) and/or beam/vacuum processing. However, the total energy consumption of all these possessing routes should be the lowest in aqueous systems, because a much larger excess of energy is necessary to create melts, vapor, gas or plasma than to form an aqueous solution at the same temperature (Fig. 1). This idea can be easily demonstrated, using the simple example of BaTiO3. The energy diagram for the formation of BaTiO3 from various precursors is shown in reference 4. The driving forces (AG) for representative synthesis reaction of (1), (2), (3), (4) and(5) are 38, 727, 3685, 17 and —14kcal/mol, respectively at room temperature. 6' 7"

Jan 1, 2000

By Chao Li, Hongxu Li, Yang. Xie, Meng Wang, Xiangxin Hao

"With the development and utilization of resources of gold, high quality gold mine resources gradually exhausted, and refractory gold ore has become the main raw material for gold smelting, while the smelting pollutants impacting on the ecological environment is growing, in recent years there have appeared several methods of green extraction of gold such as bio-oxidation. In this paper, the life cycle assessment models about three different gold extraction technologies have been put forward. Material consumption, energy consumption and emissions during each gold production process are analyzed by using GaBi 6 software, and the environmental impact of each process is also evaluated by means of CML2001 methodology. Calculation and analysis results show that the energy consumption and material consumption are the main factors causing the environmental load; and the environmental impacts of the production process mainly attribute to the category of greenhouse effect, resources consumption and environmental acidification. Based on the evaluation, some optimization tips are proposed.IntroductionOver the past decades, as the industry policy environment continues to improve as well as gold exploration and mining smelting capacity continues increasing, gold production shows a prospecting tendency. With the wide use of gold, the demand for gold is growing, while easy smelting gold mine resources become exhausted and refractory gold ore has become the main raw material for gold smelting. In addition, pollutants impact on the ecological environment is also growing year after year.LCA (Life Cycle Assessment) makes evaluation of product “from cradle to grave” as its whole process, up to finding the sources of environmental impacts and solutions, to comprehensively account the use of resources and lower emissions. In the industrial field, life cycle can compare different technologies from different aspects of resource use, energy consumption and environmental emissions [1]. In recent years, using LCA to evaluate metallurgical industry process also has more development. The paper mainly uses LCA and scenario analysis for the gold metallurgical process by GaBi 6, to investigate the environmental impact of three different technologies of gold extraction metallurgical process. The established three evaluation models include the hydrometallurgical, pyro-metallurgical processes and bio-oxidation pretreatment methods respectively. Several environmental indexes would be selected to evaluate the environmental impact in order to find which process has smallest environmental load and some suggestion of reasonable way gold resource utilization."

Jan 1, 2014

By Thomas M. Harris

Cation exchange is not sufficiently selective to be used for the removal of heavy metal ions from a general industrial wastewater. However, if the metals can be converted to polyvalent anions through complexation, they may be removed both selectively and efficiently by anion exchange. This approach, referred to as chelation-assisted anion exchange (CAAE), has been examined using industrial wastewater samples contaminated with Ni2+ and Cr3+. For this particular application, the Ni2+ is complexed with 8-hydroxyquinoline-5-sulfonic acid, and the Cr3+ with sulfosalicylic acid. Removal efficiencies and adsorption isotherms for both the complexants and the complexes were determined in batch-mode tests.

Jan 1, 1994

By James A. Sommers

Combustion of niobium nitride powder in a stream of oxygen results in several niobium oxide phases, depending upon reaction parameters. Under rapid oxygen flow, the oxidation produces a molten mass which coalesces into droplets of ca. 2 mm dimension and effectively quenches to leave NbO2 and other lower oxides of niobium, despite the ambient atmosphere of oxygen. A preliminary survey of reaction parameters which govern the split between reduced and oxidized products is presented. This technique offers novel synthesis means for binary oxides when mixtures of NbN and other materials are combusted together, since the niobium moiety is generated in a molten state.

Jan 1, 1995

By Tugba Basargan Çagatay Morall, Gülhayat Nasun-Saygili

"The aim of this study is to prepare the apatitic material using colemanite mineral (2CaO.3B2O3.5H2O) which was obtained from Eastern Anatolia, Turkey. For this purpose, colemanite mineral was reacted with different phosphate sources, namely, dipotassiumhydrogen phosphate, ammoniumhydrogen phosphate and ortophosphoric acid at various temperatures and time periods. Experiments were run in batch system. The apatitic material was prepared by a wet method and followed by heat treatment at various temperatures. Structure of the samples was analyzed by XRD, FTIR, XRF and SEM. The particle size analysis was also made for the result product. The experiments showed that reaction temperature, contact time and heating temperature are important parameters to transform the colemanite into apatitic structure. Reaction of colemanite with dipotassiumhydrogen phosphate and ammoniumhydrogen phosphate results in amorphous, non-stoichiometric hydroxyapatite type structure, while acid based phosphate source gives brushite and monetite type product before and after heat treatment, respectively.IntroductionBoron which has properties intermediate between metals and non-metals is a member of semiconductor group of elements. Its atom is very small and has three valence electrons. Boron exists in Earth's crust (from 5 mg/kg in basalts to 100 mg/kg in shale) and in the oceans (4.5 mg/l) [1]. Turkey has 60% of world's boron reserves which is mostly in the form of colemanite (2Ca0.3B203.5H20). Colemanite is the most important calcium containing commercial borate mineral with 5 mol of crystal water [2].Calcium phosphate cements are very useful for bone repair applications because of its chemical structure. They are injectable, easy to shape and can be maintained locally. Because of those reasons calcium phosphate cements are very effective to fill bone defects with an irregular shape [3]. Hydroxyapatite (Ca10(PO)6(OHh) is the major component of the bone (70 wt%). However, hydroxyapatite stoichiometry, composition and crystallinity differ in human skeleton system [4, 5].The main objective of the present work was to study the transformation of colemanite to apatitic material using different phosphate solutions at several time spans and temperatures. The experiments were run in a batch system, change in pH and also weight loss were measured after the experiments. Several analysis methods were used to investigate the chemical and structural changes."

Jan 1, 2012

By Robert A. Reiley

Under the traditional environmental paradigm, industry, stakeholders, and government impact the environment through production, consumption, and regulation. For more than twenty years, this paradigm has survived more or less unchallenged. Environmental action has followed a typical pattern: industry pollutes, the public clamors, government enacts legislation, and industry expenditures for pollution-control equipment soar. In the 1990's, many groups realize that command-and-control techniques may not be the most effective method of dealing with environmental issues in the new millennium. The need for regulatory reform became apparent in the 1980's after an accident at the Union Carbide plant in Bhopal, India. In addition, the prospects of an integrated European market and increased global trade sparked a need for common standards regarding the production of goods and services, which led to the adoption of the International Standards Organization (ISO) 9000 Quality Standards. These factors, and others, triggered the development of the Environmental Management System (EMS). Over the past decade, country-and industry- specific EMSs were developed. However, the IS0 realized the need for a single, internationally recognized standard that would be workable for any type organization. The goal of this standard is to promote economic competitiveness, remove trade barriers, and promote environmental protection. To this end, the IS0 14000 Standards were developed to provide business with a structure for managing environmental impacts. This article argues that a new paradigm has begun to transcend the old. Protection of the environment if shifting from "government drivers" to "market drivers". This shift means that industry and stakeholders, instead of government, are taking the lead to develop ways to protect the environment. This article also argues that government can use this new paradigm, in a time of declining budgets and regulatory reform, to continue to protect the environment through increased compliance monitoring and rigorous enforcement. Specifically, the IS0 14000 Standards can allow the government to reduce compliance costs, streamline permit and reporting requirements, and provide business with regulatory flexibility. Finally, this article argues that IS0 14000 will be central to the regulatory reform effort, because it can be internally implemented with little need for legislative intervention.

Jan 1, 1999

By Fan Xiao-Hui, Jiang Li-Juan, Chen Xu-Ling

"In order to solve air leakage of sintering testing cumbersome, inaccurate results, and other issues, the sinter machine air leakage characteristics were studied, and combining the mathematical modeling and the field detection. The temperature before air leakage was calculated by mathematical model, energy balance equation was established according to sintering process, using Adams prediction correction method which has stronge stability and high precision, to solve hyperbolic partial differential equation with astringency problem. The temperature after air leakage is detected by instruments, according to energy conservation calculation the sintering air leakage rate. According to the sintering continuity and periodicity, sintering air leakage location diagnosis expert system was established to judge specific air leakage locations.IntroductionStrengthening of modern blast furnace production depends on the quality of the raw material preparation to a large extent [1]. Technical and economic index of modern blast furnace production is advanced; the most important reason is the use of concentrated feed. Sintering plant is the ""kitchen"" of blast furnace’s concentrate. As we all know, sintering plant is major energy consumption of steel plant, in sinter process energy consumption, the solid fuel consumption of total energy consumption is 75%~80%, power is 13%~20%, ignition and combustion is 5%~10%. To reduce the air leakage of sintering plant is an effective measurement to save energy consumption. At present, our air leakage of sintering compared to the other developed countries is still a long way to go. Japan’s air leakage rate is about 30%, and 35%~60% air leakage of sintering machine at home, a big gap exists between the plants. At present the determination of air leakage is all for manual operation, long measuring period, considerable manpower and resources, and the results are significantly affected by operation. For air leakage of sintering control lag issues, research and development of diagnosis expert system for on-line monitoring model for air leakage and, through this research can reduce the use of detection equipment, detect sintering air leakage, improve the yield and quality of sintering production, reduce energy consumption, and extend equipment life span."

Jan 1, 2012

By S. S. Babu, T. Hong, T. DebRoy, S. A. David

"Oxide inclusions form in welds because of deoxidation reactions in the weld pool. These inclusions control the weld microstructure development. Thermodynamic and kinetic calculation of oxidation reaction can describe inclusion characteristics such as number density, size, and composition. Experimental work has shown that fluid-flow velocity gradients in the weld pool can accelerate inclusion growth by collision and coalescence. Moreover, fluid flow in welds can transport inclusions to different temperature regions that may lead to repeated dissolution and growth of inclusions. These phenomena are being studied with the help of computational coupled heat transfer, fluid-flow, thermodynamic, and kinetic models. The results show that the inclusion formation in steel welds can be described as a function of the welding processes, process parameters, and steel composition.IntroductionThe relationship between inclusions and formation of a high-toughness phase, namely acicular ferrite in low-alloy steel welds, is well known (1-4). Past research has focused on maximizing acicular ferrite amount in welds by controlling welding processes, process variables, and welding consumable parameters. Research has shown that there is a complex interaction between inclusion characteristics, prior austenite grain size, and weld metal hardenability. In a low-alloy steel weld, the small addition of titanium lead to a change in the inclusion composition and resulted in a transition in the microstructure from bainitic to acicular ferrite [see Fig. I]. This in turn lead to the best combination of strength and toughness. This paper describes the inclusion formation in low-alloy steel welds."

Jan 1, 1999

By Ma Keyi, Yang Xianwan, Zhu Xiaoyun, Guo Zhongcheng, Zheng Yanping

"The oxidation of the Multifunctional Electrodeposited RE-Ni-WP- SiC Composites at high temperature is investigated. The results show that during high temperature oxidation the relationship between the mass change of pure Ni , Ni-W-P, Ni-W-P-SiC or RE-Ni-W-P-SiC coating and the oxidation time follows a mixed curve, i.e. it is approximately a linear relationship when the oxidation time is less than 60 mins while it is a power function relationship when the oxidation time is over 60 mins. The order for the oxidation rate of the four coatings is Ni> Ni-W-P> Ni-WP- SiC>RE-Ni-W-P-SiC. The mass change of Ni-W-P, Ni-W-PSiC or RE-Ni-W-P-SiC coating increases exponentially with a rise of oxidation temperature. The high temperature-oxidation resistance of RE-Ni-W-P-SiC composite coating is 3-4 times that ofNi-W-P alloy coating. The cross section morphologies and Xray diffraction patterns indicate that the high temperature oxidation resistance of RE-Ni-W-P-SiC composite coating is better than any other coatings.1. IntroductionWith the rapid development of modem industries the products in engineering industry are continually challenged by the requirements of long-term and stable working at higher temperature, pressure, speed and under adverse conditions. Consequently, the surface properties of the products, such as the resistance to oxidation at high temperature, the resistance to wear and the resistance to corrosion, should be improved continually."

Jan 1, 2000

By Doon Gibbs

In this talk, we review highlights of x-ray magnetic scattering studies performed during the last decade, concentrating at the beginning on experiments on the rare earth metal holmium.(1-4) Besides intrinsic interest in the x-ray scattering cross-section and its description, studies of this type are motivated by the possibility that new structural and magnetic properties of rare earth metals might be revealed, and that new techniques may thereby be developed. As a result, interest in x-ray magnetic scattering experiments. has grown rapidly during the last 10 years particularly, with the regular application of synchrotron radiation techniques- Magnetic scattering experiments have by now been performed at most of the x-ray synchrotrons around the world. In addition, insertion .device beamlines dedicated to x-ray magnetic scattering experiments are planned at each of the next-generation storage rings presently under construction in the United States (APS), Europe (ESRF), and Japan (SPRING-8). Generally, the results of x-ray magnetic scattering experiments may be analyzed within two regimes of the incident x-ray energy, namely, in the limit of high x-ray energies, when the incident x-ray energy lies above the excitation energy of any absorption edge, and at resonance, when the incident energy lies near an absorption edge. In the high energy limit, the amplitude for x-ray magnetic scattering has the simple form [L(Q)?A + S(Q)?B](5-7) Here, L(Q) and S(Q) refer to the Fourier 'transforms of the atomic orbital and spin magnetization densities, respectively, and the vectors A and B depend on the incident and scattered wavevectors and on the: incident and scattered polarization vectors. 7) Because the vectors A and B are not identical, the polarization dependence of the orbital contribution to the magnetic cross-section differs from that of the spin contribution. This leads to the possibility that the orbital and spin magnetization densities maybe distinguished, in x-ray scattering experiments. The same distinction is not directly possible by neutron diffraction techniques (in dipole approximation, where the polarization dependence of the orbital contribution is identical to that of the spin contribution), and is important to a fundamental understanding of the electronic structure of magnetic materials. A particular

Jan 1, 1992

By M. C. Ruiz

The conventional pyrometallurgical methods to treat copper sulfide concentrates include generally, one or more oxidizing steps where the formation of SO2 gas can not be prevented. From the economical point of view and the nature of some of the processes in which SO2 is produced, its complete capture is not feasible; therefore an important fraction is released to the atmosphere as fugitive emissions. In this research, the reduction of chalcocite was studied in the presence of lime as an alternative method, which overcomes the pollution problems related to SO2 emissions. The effect of temperature, time, concentration of carbon and CaO on the reduction rate were studied. Among these variables, temperature affects most the reduction rate. Conversions over 95 % can be obtained in less that 20 minutes at temperatures over 1000 ° C. The measured partial pressures of the gaseous components indicated that the chalcocite reduction proceeded through the gaseous intermediate species CO, C02, and the overall kinetics was controlled by the Boudouard reaction. The kinetic model In(1-X)= kt fits well the experimental data. Apparent activation energy of 3 14 kJ/mol was calculated for the temperature range of 900 0C-1050 °C.

Jan 1, 1999

By George Grandy

Kvaerner experience is being used to develop software to design or simulate crushing and screening plants. The model techniques discussed are presently being used for open-circuit plants and are being extended to closed circuit plants. The program contains a library of routines, each representing a piece of equipment or unit operation, which are assembled into one of several open-circuit plant configurations. Routines include gyratory primary crushers; standard secondary and shorthead tertiary cone crushers; single, double or triple deck screens; and stockpiles, feed bins and belt conveyors. The program uses steady-state models to simulate the performance of crushers and screens that have small residence times and quickly reach equilibrium when operating conditions and/or parameters are changed. The dynamic aspect of the total circuit model concerns the storage units within the circuit, i.e. stockpiles and bins, and, in the closed circuit configuration, circulating loads and size distributions. In many cases, just vendor's catalog data are necessary for a pre-feasibility simulation; in other cases, actual plant test data are required to obtain more accurate simulations. The entire plant is shown in a single graphic screen so the user can see all the relevant information he might want, and soft-keys are provided for the user to make on- line parameter changes and observe the effects on storage elements, equipment feed rates and the final product size distributions. The model also reports equipment utilization in percentage, power consumption, and other related operating information, and soon, will be able to report estimated capital and operating costs.

Jan 1, 1999

By A. V. Tarasov

The high efficiency of autoclave processes is attributed to the fact that they are suitable for processing of refractory raw materials, have low capital costs and high productivity, ensure integrated utilization of the feed materials, produce innovative saleable products, completely eliminate any air emissions, provide low-waste or waste-less technology, as well as mechanization and automation of production processes. In the immediate future, it might be expected that autoclave processes will find use on commercial scale for production of heavy non-ferrous metals in combination with other processes (hydrometallurgical, upgrading, sorption and solvent extraction, electrolytic, etc.) to ensure: -Integrated processing of refractory ores and concentrates (pyrrhotite, zinc, copper-zinc, lead-zinc, nickel-cobalt, copper, pyrite); -Production of metallic powders of base metals as commercial products (copper, cobalt, nickel, etc.), composites on their bases, final products and saleable salts. Processing technologies incorporating autoclave processes, especially, at the stage of liberation (chemical upgrading) of minerals, are characterized generally by high overall recoveries of valuable constituents significantly exceeding recoveries common for conventional pyrometallurgical processes (for some elements by several tens of percent). An example is processing of low-grade refractory pyrrhotite concentrates using autoclave liberation of feed material under pressure of a new reagent, i.e., sulfur dioxide. The use of sulfur dioxide ensures a significant improvement in the recoveries of non-ferrous metals and platinoids to sulfide concentrate and smelting of the latter increases the capacity of the smelting units employed and minimizes the yield of discard slag and loss of metals in slag; in addition, it resolves the problem of sulfur dioxide utilization.

Jan 1, 2003

By Norberto Benitez, Christian Ludwig, Simona Regenspurg, Fabian Mendez

"Navarro is the main garbage dump in the city of Cali (Colombia). Operated since the late 1960s it collects about 1.600 tons of waste daily. The environment surrounding Navarro is highly contaminated and the pollutants released by the dump threaten human health in the adjoining neighborhoods. The goal of our project is to identify major pollutants released from the dump and their distribution in the surrounding ecosystem. In a first phase of the sampling and analysis program landfill leachate was collected and screened for heavy metals and for the most common persistent organic pollutants. This allowed us to identify the most relevant compounds on which we focused in a more detailed second phase investigation. These compounds were quantified in the vicinity of the landfill (groundwater, surface water, drinking water and soil) to get information on their mobility and possible pathways into the human body.IntroductionThe usual technique of waste disposal in most developing countries is by landfilling on not -, or not well controlled sites, where people live close by or even on the waste itself. A typical example for this practice is Navarro, the main garbage dump in the city of Cali (Colombia). Operated since the late 1960s it now consists of about 23 million tons of household and industrial waste. The dump is located on a wetland in the riverbed of the Cauca River, the main drinking water source for Cali. Two ponds of unknown permeability located next to the landfill collect a fraction of the waste leachate. During the rainy season, the ponds frequently overflow and drain into the soil (alluvial, loamy sediments) of surrounding sugar cane fields. The environment of Navarro is assumed to be highly polluted and there is evidence that it affects the health of nearby inhabitants. Specifically, the incidence of respiratory diseases was higher among vulnerable individuals (<3 and >50 years old) living in a <3 km perimeter of Navarro as compared with a control group (Solano et al., 2006). Further, a clustering of extremely rare congenital malformations (sirenomelias and cyclops) was observed in a small area during a short time period (<6 months) (Filigrana et al., 2008)."

Jan 1, 2008