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The decomposition of pyrite was investigated in a thermo‐balance. In neutral or reducing gases it decomposes between 550° and 700°C to volatile sulfur and ferrous sulfide. In oxygen it oxidizes in two stages: between 445° and 520°C, it forms sulfur dioxide and ferrous sulfide: between 610° and 660°C. it forms more sulfur dioxide and hematite'In air Or with fast cycles, the reactions ...
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The kinetics of organic sulfur removal from coal by oxidation in an alkaline solution and the associated problem of chemical analysis for organic sulfur in chemically treated coal were also investigated. Moreover, since alkaline leaching methods tend to convert iron pyrites into more magnetic substances such as hematite or magnetite, the
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Zyryanov et al., 2011). Oxidation of the pyrite (FeS 2) in pulverized coal at high temperatures produces molten iron spheres and sulfur, the iron oxidizes to form magnetite (Fe 3 O 4) and hematite (Fe 2 O 3) as common constituents in fly ash (Flanders, 1994). Iron plant oxides in coal ash may occur in many forms, including dendritic
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coal, magma activities led to that high temperature pyrolyses pyrite with H2S or SO2 formed and excluded,and native surface morphology features of pyrite will also be strongly transformed [13] ; coal-pyrite begins to release H 2 S and SO 2 gas 400-600 °c, and gradually changes to meteorite sulfur
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Pyrite is a good example of this because the pyrite oxidation process and the geochemical evolution of sulfur are controlled by reactivity reactions, ... such as magnetite (Fe 3 O 4), hematite (Fe 2 O 3), iron (ferric or ferrous) sulfate ... S. TG–FTIR and kinetics of devolatilization of Sulcis coal. J. Anal. Appl. Pyrolysis 2013, ...
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Pyrite's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold.The color has also led to the nicknames brass, brazzle, and Brazil, primarily used to refer to pyrite found in coal.. The name pyrite is derived from the Greek πυρίτης λίθος (pyritēs lithos), "stone or mineral which strikes fire", in turn from ...
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Abstract. Despite the great abundance of pyrite in nature and its role as one of the main sources of SO 2 emissions in industrial processes, there is little definitive information about the kinetics and mechanisms of pyrite oxidation and decomposition reactions. This work aimed to determine the viability of applying the Friedman method for kinetic parameter determination to the oxidation and ...
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electrum and native gold associated with silver sulfosalts, and with magnetite and base metal sulphides, including pyrite …Redox (reduction–oxidation, pronunciation: / ˈ r ɛ d ɒ k s / RED-oks or / ˈ r iː d ɒ k s / REE-doks) is a type of chemical reaction in which the oxidation states of atoms are changed.
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The decomposition of pyrite was investigated in a thermo-balance. In neutral or reducing gases it decomposes between 550° and 700°C to volatile sulfur and ferrous sulfide. In oxygen it oxidizes in two stages: between 445° and 520°C, it forms sulfur dioxide and ferrous sulfide: between 610° and 660°C. it forms more sulfur dioxide and hematite'In air Or with fast cycles, the reactions ...
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Thermal oxidation of pyrite as in a mine fire (Cisowski 1987) or chemical oxidation of pyrite as in a site producing AMD (Henderson 1984) results in the formation of magnetic minerals. Under proper conditions, these magnetic minerals can be detected and their distribution mapped through magnetic …
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According to the XRD results, the phase transition of the pyrite starts at 350 °C, pyrrhotite and magnetite are intermediate products of the oxidation from pyrite to hematite.
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A project was undertaken to characterize the oxidation of iron pyrite to the non-slagging species magnetite during pulverized coal combustion. The work was aimed at defining the pyrite transformations responsible for the higher slagging propensity of staged, low-NO{sub x} pulverized coal combustor burners.
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Pyrite oxidation has been studied extensively, in the past, because of its importance in sulfide mineral separations by flotation, in the generation of acid in mine waters and in leaching of pyrite. The oxidation of pyrite also plays key role in supergene alteration of ore deposits, the formation of acid sulfate soils, etc. Pyrite oxidation is ...
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Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe 3 O 4.It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. It is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of ...
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the pyrite/pyrrhotite interface is the controlling step [5]. The present work aimed to determine the viability of the application of the Friedman isoconversional method for the determination of the kinetic parameters of the oxidation and decomposition reactions of pyrite from the coal mining industry. The activation energy (E a), the pre ...
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Investigation of the alteration processes of pyrite revealed that several magnetic chemical species are formed, depending upon oxygen and sulfur fugacities, temperature, and ph. Oxidation in both a dry and aqueous environment was studied. The primary purpose of the work included attempts to understand the processes wherein magnetic substances can be created from pyrite with the ultimate goal of
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Mixing magnetite with pyrite or with coal resulted in a reverse selectivity, that is, the nonmagnetic fraction of the coal had more sulfur. Steam-air treatment of the mixtures showed no promise at all. ... Thus the required overall degree of oxidation of pyrite …
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The model follows the particle composition history, starting from pyrite decomposition to pyrrhotite (Fe1 − xS), and its subsequent oxidation to a molten sulphide-oxide mixture, then magnetite ...
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To obtain a suitable build-up of Fe304 from pyrite in coal, therefore, the coal should be Oxidation of pyrite in coal to magnetite: A. N. Thorpe et al. heated to a relatively low temperature (390-408) at a low partial pressure of air (1.6-2.4 kPa).
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Unformatted text preview: OXIDATION ROASTING OF A COPPER SULFIDE ORE INTRODUCTION Pyrometallurgy deals with the heat treatment of ore, which lead to physical and chemical transformations of the minerals and allow the extraction of valuable metals.Chalcopyrite is a brass-yellow mineral with a chemical composition of CuFeS2. Roasting is essentially a surface reaction in which the oxide layer ...
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When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393-455 ??C, pyrite (FeS2) in coal is partially converted to magnetite (Fe304). The maximum amount of Fe304 formed during the time of heating corresponds to 5-20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains.
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Pyrite (FeS2) inclusions in coal, when heated in an oxygen deficient atmosphere (approximately 1% oxygen), become coated with magnetic Fe3O4 due to oxidation. Most of the FeS2 can thus be removed from the coal by magnetic separation to reduce the sulphur concentration. The oxidation products have been studied in greater detail by measuring the SO2 and O2 in the effluent gas during the heating ...
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1. Introduction. Pyrite, a mineral with a chemical formula of FeS 2, is an iron disulfide, which is usually associated with other sulfides and oxides.It is abundant in the earth's surface, being found in the composition of sedimentary and metamorphic rocks, in coal beds and as a replacement mineral in fossils (Klein and Hurlbut, 1993).There are occurrences of high crystallinity pyrite in the ...
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This study presents a numerical model to simulate a long-term pyrite oxidation process and subsequent multi-component reactive transportation of the oxidation productions in an abandoned coal waste pile in Northeast of Iran. For this purpose, 240 solid samples of wastes were obtained from different depths of 10 vertical trenches excavated in the pile. Then, geochemical analyses, including ...
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The roasting of pyrite grains proceeds according to a shrinking core model, leaving a partially reacted grain with a core of unreacted pyrite and a shell or rim of mainly hematite or magnetite and ...
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Thermochim Acta 1989;145:115–30. [28] Dunn JG, De GC, O'Connor BH. The effect of experimental variables on the oxidizing environment conducive towards formation of magnetite mechanism of the oxidation of pyrite: part 2. Oxidation of particles of size 90– and hematite.
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The sulfur content of coal treated in accordance with this method can be reduced by subjecting the treated coal to a low-strength magnetic field for moving at least 50% by weight of the pyrite from the coal although a smaller fraction, about 5 to 25%, of the pyrite is actually converted to magnetite.
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Pyrite FeS. 2 Magnetite Fe. 3. O. 4 . Temperature, ºC . HSC calculation . 1. 400-500 ºC pyrite no significant decomposition 2. 600 ºC pyrite & pyrrhotite significant decomposition 3. 700-800 ºC pyrrhotite stable phases 4. 900 ºC pyrrhotite & Magnetite commencement of oxidation
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Clay and pyrite transformations during ignition of pulverised coal - Volume 48 Issue 347. ... Oxidation of pyrite leads to coating of cenospheres by condensed magnetite and the emission of sulphur dioxide in the flue gases. Type Research Article.
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When bituminous coal is heated in an inert atmosphere (He) containing small amounts of oxygen at 393–455 °C, pyrite (FeS 2) in coal is partially converted to magnetite (Fe 3 0 4).The maximum amount of Fe 3 0 4 formed during the time of heating corresponds to 5–20% of the total pyrite present, depending on the coal sample. The magnetite forms as an outer crust on the pyrite grains.
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The thermal phase transition of pyrite from coal was studied using thermogravimetry and derivative thermogravimetric, infrared spectroscopy and X-ray diffraction (XRD). According to the XRD results, the phase transition of the pyrite starts at 350 °C, pyrrhotite and magnetite are intermediate products of the oxidation from pyrite to hematite. It was proposed that the main gases and volatile ...
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Pyrite (FeS 2) inclusions in coal, when heated in an oxygen deficient atmosphere (approximately 1% oxygen), become coated with magnetic Fe 3 O 4 due to oxidation. Most of the FeS 2 can thus be removed from the coal by magnetic separation to reduce the sulphur concentration. The oxidation products have been studied in greater detail by measuring the SO 2 and O 2 in the effluent …
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