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By Fathi Habashi

The behavior of pyrite, covellite, and arsenopyrite during leaching is different from other sulfides due to the presence of the disulfide ion, Sl. Arsenopyrite contains in addition, the diarsenide ion, Asl. The disulfide ion undergoes auto-oxidation in high acidity leading to elemental sulfur and sulfide ion formation: The sulfide ion may oxidize further by oxygen to elemental sulfur if high acidity is maintained. In neutral medium, the disulfide ion does not undergo auto-oxidation but oxidizes to thiosulfate then to sulfate: This leads to the two overall reactions observed experimentally: In acid medium and in neutral medium Covellite and arsenopyrite behave similarly.

Jan 1, 1995

By Geza Kisvarsanyi

Ore deposits composed of enargite, tennantite, gold, and pyrite have been mined in volcanic rocks of Oligocene age (35 m.y.) at Recsk, Hungary. Vertical and horizontal zoning of the alunitic-argillic alteration and of the ore minerals led to the concept of an intrusive heat source at depth. Subse-quent drilling disclosed a series of ore deposits in a zoned pattern in and around a stock, separated by a barren gap of 1000 meters from the shallow ore. The ore system is in a intracaldera horst-graben structure, formed by collapse and intrusion in a microplate subduction. volcanic-arc tectonic environment.

Jan 1, 1987

By B. Boryczko, J. Norwisz, Jose Escobedo Bocardo, Z. Kolenda, A. Holda

"Classical thermodynamic analysis of any thermal and chemical process is usually based on the first law of thermodynamics. Such an approach is not sufficient when deeper understanding of the nature of each elementary process is required. The use of the first and second law of thermodynamics together is necessary to solve practical process more effectively. Enthalpy and exergy balances allow to enhance our understanding of thermal processes especially when cumulative consumption of energy and exergy is calculated. To ensure reliability of such an analysis the least squares method for adjustment of mass balances of principal chemical elements has been applied and described in detail. Numerical analysis has been carried out to compare two different processes of copper production – shaft furnace and flash smelting.IntroductionClassical thermodynamic analysis of any technological process is usually based on the First Law of Thermodynamics in the form of energy (enthalpy) balances. Such an approach is useful in engineering practice as it makes analysis easier in the global scale neglecting modeling of the elementary processes, allows calculation of the thermal efficiency and makes possible to control quality of the measurement results. Additionally, graphical presentation of the energy balance is simple in the form of Sankey diagram.In the case of aluminum electrolysis process, design of the new electrolyzer or its modernization is always based on the enthalpy balance.However, deeper thermodynamic analysis leads to the conclusion that such an approach is not sufficient. The First Law of Thermodynamics guarantees the exact equivalence of the various forms of energy (allowing all forms to be measured in the common unit such as joules) but it does not guarantee interconversibility. Thermal energy (heat) is in a peculiar and unique position, for whereas all other forms can be completely converted into thermal energy, the reverse process id impossible, only a portion of the heat can be converted into mechanical energy. Explanation comes from application of exergy balances. As we know exergy expresses the amount of mechanical work necessary to produce a material in its specified state from components common in the natural environment, in a reversible way, heat being exchanged only with environment [1]. Consumption of exergy connected with the fabrication of some considered product appears not only in the plant manufacturing the product, but also in all plants delivering raw materials for the final production process"

Jan 1, 2008

By R. Boussaa, Y. Fautrelle, K. Zaidat, O. Budenkova, B. Saadi, X-D. Wang, L. Hachani, H. Ben Hadid

"Comparison of experimental data obtained in a benchmark experiment of solidification of a Sn-3%wt.Pb ingot and numerical results of two-dimensional and three-dimensional simulations of the process is presented. The benchmark experiment consisted in solidifying a rectangular ingot of Sn-3%wt.Pb alloy using two heat exchangers. Conditions of solidification were thoroughly controlled due to six thermocouples embedded into each heat exchanger. Due to another array of thermocouples the evolution of the temperature field at a lateral wall of the crucible was registered during the whole experiment. A treatment of the temperature data provided an estimation of the velocity field in the experiment. Post-mortem analyses of the sample provided the pattern of macrostructure of the sample and qualitative segregations pattern. 2D and 3D numerical solidification models are developed to give the distribution of the solute in a solidified sample.IntroductionConvection, either natural or forced, plays a very important role during the solidification. Its intensity and flow pattern affect heat and mass transfer and, consequently, macrostructure and segregation in a solidified ingot [1-4]. The effect of buoyancy convection during solidification has been studied in many laboratory-scale experiments [5-6]. Due to these experiments a general comprehension of formation of various defects in the ingot has been achieved. However, mentioned studies were not consistent since alloys, solidification conditions and configurations were every time chosen arbitrary. That is why the role of each parameter characterizing solidification process remains unclear. Moreover, the question of reproducibility of defects under the same solidification conditions still exists. In addition, most of the experiments suffer from the insufficient knowledge of control parameters that makes difficult their use for validation of models for solidification. These parameters serve as boundary conditions for numerical modeling and their incomplete description leads unavoidably to the errors in simulations. This situation motivated us to develop a setup for benchmark solidification experiments and to perform a set of the solidification experiments which we reported in [7]. Here we presented a comparison between results obtained in a benchmark experiment of solidification of Sn-3%wtPb ingot and its numerical modeling, which was performed in two-dimensional and three-dimensional configurations."

Jan 1, 2012

By T. T. Chen, J. E. Dutrizac

"Grooved cast Pb-Ag anodes are used by some zinc refineries to improve current efficiency. It was found that the manganese oxide scale formed on a grooved Pb-0.75% Ag anode consists mainly of MnO2, which occurs characteristically in rhythmically banded colloform structures and adheres to a layer of ""Pb02+PbS04"" that oxidized from the anode. The relatively homogeneous and nearly fracture-free morphology of the ""Pb02+PbS04"" layer suggests the relatively uniform corrosion of the anode. Deposition of the Mn oxide initially follows the contours of the anode surface, but the grooves eventually become filled with Mn oxide and gypsum. Hydrous Mn oxides and amorphous Mn oxides are believed to be also present in the manganese oxide scale. Tiny particles of PbS04 and SrS04, together with gypsum, other impurities and micro-pores, tend to concentrate in the grooves.IntroductionManganese is a common impurity in hydrometallurgical zinc processing circuits. The manganese originates from sphalerite (Zn,Fe,Mn)S and from the Mn02 added to the leaching circuit to oxidize ferrous ions [1]. Manganese in the sphalerite follows Zn through the roasting, leaching and purification processes, and is present as Mn(II) in the purified ZnS04 solution. The Mn in the added Mn02 is reduced to Mn(II) during the oxidation of the ferrous ions present in the leach solutions. In both cases, MnS04 is generated, and the MnS04 accumulates in the purified solution. In the cellhouse, Zn is plated at the cathodes to produce high quality metal. The Mn(II) is partly oxidized at the anode surface to Mn(IV), and the Mn(IV) precipitates as a scale on the surface of the anode and as a sludge on the bottom of the electrolysis cells. The presence of a thin layer of manganese oxide scale on the surface of the Pb-Ag anode can minimize the corrosion of lead and, accordingly, reduce the contamination of the electrodeposited zinc. However, a heavy manganese scale build-up can cause ""staining"" of the zinc deposits and reduced current efficiencies. Consequently, periodic anode cleaning to remove excess manganese oxide scale is carried out routinely in commercial operations."

Jan 1, 2011

By Mahmood Alemrajabi

When LKAB processes their iron ores in northern Sweden, they generate apatite as a by-product. The apatite has been recovered by flotation and the concentrate contains about 0.4 wt% rare earth elements (REE). Both phosphate rock and REE are listed as critical raw materials for the European union. In the present study, the recovery of REE within the nitrophosphate process of fertilizer production has been studied. In the first stage, the REE are precipitated and isolated as a phosphate concentrate. For further purification and individual separation of REE by solvent extraction, removal of phosphorous from the concentrate to enhance the dissolution of REE in mild acidic solutions is essential. In this study, thermal treatment of the concentrate with sodium hydroxide at elevated temperatures followed by water leaching has been studied in order to separate the phosphorous and thereby facilitate dissolution of the REE. The results show that 95% of total phosphorous initially present in the REE phosphate concentrate is removed after thermal treatment with NaOH 1:1 mass ratio, at 400 °C.

By Luiz R. P. De Andrade Lima

This paper presents a mathematical model for the oxide copper ore heap leaching process. The data used in the model include physical-chemical, .geometrical and operational data, as: leachable metals ore contents, .flow rate and acid concentration, parameters of passivity, ore size distribution, the average residence time of the solution in the heap, height, irrigated area and weight of ore in the heap. In this model the heap is divided into horizontal and plane layers of constant area. The flow of the liquid in the heap is considered unidirectional and the solid-fluid reaction model is considered under diffusive control. The average residence time of the solution into the heap and the apparent effective diffusivity of the acid through the ore particles have .a significant influence on the rate of the copper extraction and its concentration in the pregnant solution; therefore these parameters are used in the model calibration. When this algorithm was applied to a laboratory test, the results showed that the model is adequate to predict the process performance.

Jan 1, 1999

By Nathaniel Arbiter

The first ammonia leaching plants, applied to copper carbonate and native copper tailings in 19 15, were followed more recently by research and development of flowsheets for ammonia leaching of sulfide concentrates. These were applied to two commercial plants. Anaconda's Arbiter Plant started up in 1974 with a design capacity of 36,000 tons/year of cathodes, to be produced by ammonia leaching with oxygen, followed by solvent extraction and electrowinning. The plant shutdown in late 1977 as a result of high maintenance and operating costs, partly due to harsh winters; to complications associated with sulfate disposal; and to changes in mineralogy. BHP's Coloso plant in Chile was designed to produce 80,000 tons/year of cathodes by leaching part of Escondida's concentrate production. Using a similar flowsheet but with air and low temperatures to avoid sulfate production, it started up in late 1994 and shutdown in mid-1998, after failing to reach cathode design capacity, and experiencing problems with its technology. The paper reviews the technologies and also alternative methods for overcoming the problems.

Jan 1, 1999

By M. K. Patel, K. A. Pericleous, M. Molaei

"The future trading of carbon credits and increased financial cost necessitates substantial cuts in incidental C02 emissions in the production of metals (iron, steel, aluminum, zinc, lead). Although greener methods of production are being developed, in the short term the use of point-source C02 extraction using existing technology remains attractive. Accelerated natural carbonation, in a fluidized bed is a feasible technological route investigated in this research. CFD modelling has been used to study the efficiency of C02 capture in a fluidized bed reactor containing a CaO solid sorbent. A Lagrangian/Eulerian scheme describes describe CaO particle trajectories and exchange of mass, momentum and energy with the carrier gas, with a typical off-gas composition. Different reactor geometries are considered (with uniform, stepped and gradually expanding cross-section), to maximize conversion for a given particle loading and size distribution (100-200 microns). Removal efficiencies of up to 80% are demonstrated, making this a viable process.IntroductionBased on Intergovernmental Panel on Climate Change (IPCC) reports, the major cause of climate change and global warming is due to a high level of C02 concentration in the atmosphere resulting from fossil fuel combustion, particularly in coal-fired power plants [1]. Carbon capture and storage is therefore the most important action proposed to reduce C02 from combustion flue gases. In this process, carbon dioxide is captured and may then be regenerated as pure C02 and conducted to a permanent storage, or simply stored as a solid carbonate [2]. Capture and storage of C02 has an economic penalty and the main cost of this penalty is associated with the capture plant. Capturing C02 with a lime-based solid sorbent (CaO) is a very promising technique, due to the low cost and the wide availability of the reactant. In this process, the CaO reacts with C02 based on the following reaction in a reactor called a Carbonator:"

Jan 1, 2012

By Ann M. Hagni

Flash reduction of zinc oxides is an alternative, environmentally safe method to leaching and electrowinning for zinc recovery. Zinc and lead are volatilized in a flash reactor, a non-hazardous residue is generated, and the fuel source is inexpensive coal in the flash reduction process. Results from experimental laboratory tests yielded low zinc recovery for this process. Mineralogical and textural characterization of the residues from the flash reduction tests for different feed materials and temperatures were conducted to determine the cause for the low zinc recovery. Reflected light microscopy, cathodoluminescence microscopy, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction were utilized in this applied mineralogical research. The original zinc calcine is composed primarily of fine-grained, iron-bearing zincite particles, 25-40 um in diameter, in a porous texture. Pellets processed at 1150°C were found to produce reaction rims of franklinite-magnetite-jacobsite solid solution that are 125-200 um thick and surround cores of unreacted iron-bearing zincite in a Zn-Fe-Si-Ca glass matrix. The reaction rims have subsequently oxidized to form an outer 10 ~m thick rim of hematite. Slags from calcines processed at 1275°C are primarily triangular particles with porous centers, cenospheres, and spheres of iron-bearing zincite, in addition to rectangular particles composed of non-porous franklinite-magnetite solid solution cores with iron-bearing zincite rims. Slag particles from calcine processed at 1200°C are predominantly 100-250 ~m triangular-shaped, spheres, and cenospheres containing fine-grained franklinite and franklinite-magnetite solid solution in an iron-bearing zincite matrix. Slag from calcine processed at 1300°C are also predominantly 1 00-250 um triangular-shaped, spheres, and cenospheres but contain coarser-grained iron-bearing zincite. The zincite in the penets and the slags typically contain 10-20% iron. Based upon these mineralogical observations, it is concluded that the significant amounts of iron in the zincite prevent volatilization of the zinc in the flash reduction process.

Jan 1, 1995

By James J. Komadina, Robert R. Beebe

"Heap leaching of gold ores has enjoyed wide acceptance in the arid and semi-arid regions of the western U.S., Australia and South America. There are areas, however, where cold weather or excessive precipitation can limit the usefulness of heap leaching. Even in Nevada difficulties can be encountered which call for special operating procedures.The paper discusses the general climatological limitations and some of the techniques used to extend heap leaching into colder conditions. A case history of the Cripple Creek and Victor Gold Mining Company operation in Colorado examines 'valley-fill"" technology as an ideal cold-climate solution, where topographical conditions permit.AcknowledgementsThe authors gratefully acknowledge the management of Independence Mining Company for their permission to present this paper. The contributions of Golder Associates; Pikes Peak Mining Company Environmental Affairs Department staff, and the Colorado Department of Mines and Geology were all invaluable in successfully concluding this project.BackgroundWhen heap leaching of oxidized gold ores was introduced in the rnid-1970s it was aimed at large tonnages of low-grade material which could not, in general, be developed via conventional milling. Normally, the reasons for this were economic rather than technical: capital and operating costs for milling were simply too high. At first, grade was almost the only criterion, but deposits too small to justify milling were also potential targets for heap leaching.Renewed interest in gold was centered in the western United States and Australia, where exploration for milling-grade deposits had never really died. When heap leaching came along, it was in these areas that the first developments took place. Coincidentally, these same areas were favorable for heap leaching: climates were temperate for most of the year and competing land uses were limited. Even so, in the western United States in particular, winter temperatures were low enough to complicate operations. Precipitation was less a problem, although heavy snowfalls could periodically interfere as well."

Jan 1, 1997

By Wilky Desrosin, Alicia E. Ares, Carlos E. Schvezov

"In the present research the horizontal directional solidification Zn-Sn alloys (Zn-4wt. %Sn, Zn- 6wt. %Sn, Zn-10wt.%Sn and Zn-30wt.%Sn) was carried out by extracting heat in two opposite directions. For this purpose, ceramic molds, a muffie, a horizontal furnace with two heat extraction systems at the ends, a measurement, acquisition and recording temperature system, eight K-type thermocouples and an electronic recorder were used. The main parameters involved in the columnar-to-equiaxed transition, CET, were: the moment of start and end of solidification at each position under consideration, cooling rates, the average temperature gradients and critical temperature gradients at the CET, the average speed of liquid and solid interphases left and right, advancing in opposite directions. Also, solidification kinetics was found to be different between horizontal solidification two-way heat extractions, with preliminary results of the vertical unidirectional solidification. In the solidification experiments, the velocity and accelerations of the liquidus and solidus interphases usually occurs at the end solidification zone of the samples.IntroductionSolidification of metal alloys, which starts in the external equiaxed region (chill), results in two basic types of structures in a single solidified alloy sample: columnar and equiaxed. The presence of both structures indicates the occurrence of the colunmar-to-equiaxed transition phenomenon[!].Studying the colunmar-to-equiaxed transition, CET, is of great technological interest for the evaluation and design of the mechanical properties of the solidification products. To this end it is necessary to understand the mechanisms by which it occurs. As found in previous studies [2-5], the CET occurs by competition between columnar and equiaxed growth. Mainly is controlled by the parameters of casting, such as the alloy composition, the density of the present nuclei in the liquid, the cooling capacity of the metal I mold, and the degree of convection in the liquid [7-10]."

Jan 1, 2014

By Jian Li, J. Miles, P. Liu, W. Cook, W. Zheng, Alvin Qian

"High temperature corrosion resistance is one of the key challenges in water-cooled nuclear reactor material development. Iron based materials with low Cr content exhibits superior high temperature mechanical properties. However, due to the relatively low Cr content, their corrosion resistances under supercritical water (SCW) conditions are generally poor. High-Cr alloys, despite their much improved corrosion resistance, often suffer from embitterment due to the precipitation of sigma phase in the microstructure. In this study, corrosion resistance of an in-house produced high Cr steel (25%Cr) showed much better corrosion resistance compared to that of low Cr alloy (14%Cr). This high-Cr steel can potentially be used as a corrosion-resistant coating for structural materials in sew applications.INTRODUCTIONThe supercritical water-cooled reactor (SCWR) concept is one of the promising designs for the next generation nuclear reactor, in which the water coolant is designed to be at about 625°C and 25 MPa at the outlet of the reactor core. Under these relatively high-temperature and high-pressure conditions, the cooling water is at supercritical state. High-temperature mechanical properties, corrosion resistance and radiation damage are some of the key challenges. At present, no single commercial material can meet all the requirements of the severe SCWR in-core conditions. Canada supports research in several key areas of SCWR development, including materials selection. A major focus is on materials development, selection and evaluation for both in-core and out-of-core components.Allen et. al. [1] carried out a comprehensive study on the SCW corrosion resistance up to 600 °C on commercially available high temperature materials including Ni-based super alloys, various types of stainless steels and ferritic/matensitic steels. They concluded that ferritic steels develop a relatively thick but mechanically stable oxide layer, while austenitic alloys develop a thinner oxide layer that has been found to spall in some cases. Of the three types of alloys examined, the Ni-based alloys exhibited the lowest oxide thickness, however pitting was observed in the vicinity of intermetallic precipitates."

Jan 1, 2011

By Lucas Barbosa de Souza Martins, Frederico Muylaert Margem, Nathalia Carneiro Garcia Rosa, Sergio Neves Monteiro

"A natural banana fiber extracted from the plant pseudostem has shown values of density and mechanical strength with potential for uses in engineering applications such as automobile interior parts and floating components. Moreover, natural fibers can also be used as insulating materials in packaging and building panels. In this case some thermal properties are required. Therefore, the objective of this work was to evaluate the thermal behavior of the banana fiber by means of TGA, DTG and DSC analysis. The TGA curves revealed weight loss related to release of humidity and molecular structure decomposition. Peaks in the DTG curves indicated two intervals in temperature associated with different decomposition processes. The only endothermic DSC peak found was attributed to the lignocellulosic water of hydration being lost around 121°C.IntroductionIn recent times, environmental aspects related not only to pollution caused by non-degradable synthetic leftovers, specially polymeric wastes, but also to climate changes as a consequence of industrial activities, are motivating the use of natural materials. A particular case is fibrous composites, like the fiber grass composites. These synthetic materials, made from non-renewable polymers, are practically non-degradable and contribute to global warming by the CO2 emission associated with the energy required for the fabrication process. In spite of these environmental shortcomings, fiber materials are essential for the production of many items such as insulating chests, automobile cushion, construction panels, etc. An environmentally correct alternative to replace synthetic fibers composites is the naturally existing ones extracted from plants such as ramie and sisal. These have some environmental advantages of being renewable and degradable, these banana plant provide a negative contribution to C02 emission by absorbing greenhouse gas during the plant life cycle. Banana fibers have been used since long time in simple items such as ropes and rugs. Today they are used in engineering applications related insulation in building panels [2] and finish parts in automobile interior components [3]."

Jan 1, 2012

By Honorio Oliveros Gómez, Oscar Jaime B. Restrepo

"Colombia produces nine tons of electronic waste per year and there are approximately 60 tons accumulation generated in the last nine years. This work aims to establish a general methodology in the laboratory to recover gold, silver and platinum group present in electronic waste, also explore other forms of recovery of metals contained in electronic waste. We selected seven types of electronic cards present in the computers, which have their parent desoldering electronic components. Initially, we characterized the components of the cards through X-ray diffraction and SEM, to identify the metal species and composition. Tests were conducted laboratory hydrometallurgical recovery of metals. This paper proposes a methodology for laboratory-scale work.INTRODUCTIONColombia produces nine tonnes of electronic waste per year and build there in about 60 tons generated in the last 9 years [1], Computers, TVs, audio equipment, monitors, cell phones, remote controls, printers and operated toys battery, among others are part of this inventory, which mostly comes to landfills, because the lack of legislation to control the final destination of waste electrical and electronic equipment, and lack of efficient technologies to recover materials [2]. Under these circumstances which have environmental implications, technological and economic recovery is essential metals present in the electronic cards of computers, by hydrometallurgical with subsequent base metal electrodeposition [3]. Pyrometallurgical route is discarded by major implications for economic and environmental [4]. Recovery From this perspective, the determination of the metal fraction and the relationship between the different metals, using the SEM characterization techniques - BSE and XRD is indispensable [5] It follows with electrolytic dissociation processes in the leaching and electrodeposition [6], and unit operations in the laboratory to carry out successfully these processes on a larger scale. Were randomly selected computer twenty-four postcards for nine types of cards have different functions in the computer, which, through the absorption desoldering technique, they broke the resistance (thermal, surface, photoresist, power), capacitors (ceramic, electrolytic), diodes (silicon, germanium, high frequency), transistor (NPN, PNP), processors, integrated (high, medium and low frequency), the RAM card and pin parallel port serial"

Jan 1, 2011

By Felipe P. D. Lopes, Jr. dos Santos, Sergio N. Monteiro, Frederico M. Margem

"Natural fibers are gaining attention as a class of low cost, biodegradable and renewable materials that also exhibit some interesting properties for specific applications. In particular, the incorporation of some natural fibers in polymeric matrix composites is nowadays providing opportunity of manufacturing a variety of industrial items, for instance automobile interior components. Among these fibers, ramie (Boehmeria nivea) is one of the least investigated and only recently was studied as polymeric composite reinforcement. Therefore, the objective of this work was to evaluate the possibility of ramie waste reinforced polyester composites to replace conventional building materials, such as plywood, plastic boards and gypsum panels in terms of a cost-benefit analysis.IntroductionThere is a growing concern over the environmental questions that are presently affecting our society in a global sale such as climate changes and generalized pollution. Among the solutions for these questions, the replacement of energy intensive materials, especially those long term degradable such as the synthetic fibers, is already being considered [1]. As a consequence, the past decades have witnessed an increase in research devoted to new biodegradable materials obtained from natural resources mainly the biomass. Important examples are the renewable natural fibers as well as composites incorporated with them [2,3]. In addition to their friendly status with respect to the environment, well know natural fibers like jute, sisal, wood, coir, hemp and flax are relatively low cost and recyclable. In recent works [4,5], the use of these cultivated and abundant lignocellulosic fibers was investigated as the reinforcement phase in polymeric composites.Other less know lignocellulosic fibers have also been recently investigated [6,7]. These are fibers that likewise show a potential of incorporation into the polymeric matrix of composite materials. Most of these less know fibers are typical of tropical regions and, in principle, their application in industrialized composites would represent job opportunities for developing countries in Africa, South Asia and Latin America."

Jan 1, 2008

By C. Gasparrini

Mineralogy may be applied to the selection of appropriate separation techniques, as well as to assist in the evaluation of problems causing loss of metals and other economically important elements during plant processing. Mineralogic studies may thus help develop techniques to optimize metal recoveries. The present paper describes how such factors as the minerals in which the elements of interest are concentrated, their chemistry, the chemistry of the associated minerals, grain size and textural associations with other minerals in the ore, may affect decisions on separation techniques for the recovery of economic elements. A number of case studies are described in which the mineralogical observation of ore samples has revealed the cause of problems experienced in the extraction of select precious and base metals, or has been decisive in the choice of appropriate techniques for recovery.

Jan 1, 1981

By Robert J. Stevenson

The chemical variation of central North American lignite fly ash can be compared using the major and minor oxide analyses and the distribution pattern of the inter-grain chemistries of the individual fly ash have been used to illustrate the variations in bulk ,sample and individual grain chemistry. This information documents the chemical variability of the lignite fly ashes by geographic region. There is a direct relationship between grains rich in SiOa and AlaO, and in the NazO content of the grains in lignite derived fly ashes. There is also a direct relationship between grains rich in Ca0 and the MgO and SO, content of the grains in lignite derived fly ashes,. These variations are shown using CaO-SiO2-Al2O3 and CaO-Na2O-MgO ternary diagrams.

Jan 1, 1992

By Michael Meyer

In the past shredder fluff was discarded in landfills, but shrinking landfill space and the partly hazardous content of the fluff as well as its caloric value, all resulted in efforts to turn this waste problem into a an energy resource. In order to produce a fuel, the inorganic compounds have to be removed. Extensive analyses and particle size measurements were made on fluff from various shredder. For optimal separation all particles are reduced to a uniform, relatively small size. In a subsequent combined - screening and air classification - process, successful separation into organic and inorganic fractions is achieved. The inorganic fraction is treated in a heavy media or an eddy-current separator to recover the valuable metals, while the organic fraction is now suitable for thermal processing, such as fluidized bed gasification and using the resulting carbon as a chemical reagent.

Jan 1, 1995

By Hiroshi Nakajima, Kotobu Nagai, Toshihiro Hanamura

"Low carbon ferritic steel bars with ultra-fine grain structure was developed through a warm rolling for the first time by the present authors. They show better low temperature toughness than conventionally hot-rolled plates. Hence, the brittle fracture surfaces in Charpy tests were examined in terms of the effective grain size of fracture, compared with those of conventional QT steels. The ductile-to-brittle transition temperatures were in good accordance with those for the QT steels if referred to the effective grain size of fracture: · However, the size was a few times that of the ferrite grain. This means the grain refining is not yet fully utilized from the viewpoint of low temperature toughness. The anisotropy of· the impact properties and the annealing effect of highly dislocated structure on the toughness are also discussed in the present paper.IntroductionFor structural materials, both high strength and good toughness are required. Well-known approaches for obtaining better toughness for steels are as follows:1) Grain refining2) Addition of Ni3) Thin plate effect by cracking parallel to the rolling direction prior to crack propagation4) Contribution of metastable austenite.Among them, only the grain refining can raise the strength and improve the toughness. And it is well known that the finer the ferrite grain size, the lower the ductile-to-brittle transition temperature. For example, in the case of 0.11 carbon steel, the transition temperature decreases linearly to in d 1/2 [1 ]. However, these have been told in the regime of coarse grain size that is larger than 10 µm in diameter. There ~as .been no study dealing with the low temperature toughness in the regime of ultra-fine grain size with a diameter in the order of 1 µm."

Jan 1, 2000