Studies in the thermal decomposition of natural siderites in the presence of air

Dhupe, A.P.; Gokarn, A.N.

doi:10.1016/0301-7516(90)90043-x

Cited by 46 publications

(19 citation statements)

References 8 publications

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“…While the kinetics of the thermal decomposition of siderite and its solid-solutions have been extensively studied (Dhupe and Gokarn, 1990;Jagtap et al, 1992;Kubas and Szalkowicz, 1971;Zakharov and Adonyi, 1986) great care needs to be taken in interpreting the results of such studies since there are many discrepancies between datasets. The reasons appear to be two fold: first, reaction kinetics are sensitive to the physical parameters of the sample, e.g., degree of crystallinity, surface area, presence of impurities, particles size, and the degree of compaction or porosity.…”

Section: Kinetically Controlled Carbonate Decompositionbrearley (2003mentioning

confidence: 99%

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Thomas‐Keprta

Clemett

McKay

et al. 2009

Geochimica et Cosmochimica Acta

108

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The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global oceans. Intimately associated within and throughout these carbonate disks are nanocrystal magnetites (Fe 3 O 4 ) with unusual chemical and physical properties, whose origins have become the source of considerable debate. One group of hypotheses argues that these magnetites are the product of partial thermal decomposition of the host carbonate. Alternatively, the origins of magnetite and carbonate may be unrelated; that is, from the perspective of the carbonate the magnetite is allochthonous. For example, the magnetites might have already been present in the aqueous fluids from which the carbonates were believed to have been deposited. We have sought to resolve between these hypotheses through the detailed characterization of the compositional and structural relationships of the carbonate disks and associated magnetites with the orthopyroxene matrix in which they are embedded. Extensive use of focused ion beam milling techniques has been utilized for sample preparation. We then compared our observations with those from experimental thermal decomposition studies of sideritic carbonates under a range of plausible geological heating scenarios. We conclude that the vast majority of the nanocrystal magnetites present in the carbonate disks could not have formed by any of the currently proposed thermal decomposition scenarios. Instead, we find there is considerable evidence in support of an alternative allochthonous origin for the magnetite unrelated to any shock or thermal processing of the carbonates.

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Section: Kinetically Controlled Carbonate Decompositionbrearley (2003mentioning

confidence: 99%

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Thomas‐Keprta

Clemett

McKay

et al. 2009

Geochimica et Cosmochimica Acta

108

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“…The mechanisms of thermal decomposition of siderite are quite complex and depend on the roasting atmosphere. The final product, generally, is hematite (Fe 2 O 3 ) in an oxidizing atmosphere (O 2 or air), magnetite (Fe 3 O 4 ) in a CO 2 atmosphere, and magnetite and wustite (FeO) in an inert atmosphere (Chang and Ahmad 1982;Dhupe et al 1990). In an inert atmosphere, wustite is first formed during the decomposition of siderite, but wustite is an intermediate phase and transforms to magnetite in a short period of time (Kissinger et al 1956).…”

Section: Introductionmentioning

confidence: 99%

Simultaneously Roasting and Magnetic Separation to Treat Low Grade Siderite and Hematite Ores

Chun

Zhu

Pan

2014

Mineral Processing and Extractive Metallurgy Review

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During the roasting process, siderite (FeCO 3 ) transforms to magnetite (Fe 3 O 4 ) along with producing carbon monoxide (CO), but hematite (Fe 2 O 3 ) needs CO to reduce into magnetite. The process of simultaneously roasting and magnetic separation was developed to treat the low grade siderite and hematite ores without adding any reductant. Effect of mass ratio of S-to-H (siderite ore to hematite ore) on the separation indexes of iron concentrate was discussed. X-ray diffraction was also employed to detect the phase transformations of roasted ores. The technology of simultaneously roasting and magnetic separation is an effective way to treat low grade siderite and hematite ores, and also reduce the emission of CO 2 because no ruductant is added.

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“…The researches on the thermal decomposition mechanism of siderite in oxygen and inert atmosphere are mainly focused on the reaction process [8][9][10][11][12], decomposition product characteristics [10,13] and decomposition kinetics [14][15][16][17][18]. It is found that under the flow of oxygen, the oxidation is so rapid that the only detectable phase as the end product is hematite, α-Fe 2 O 3 , while magnetite and wüstite are observed in vacuum or in an inert atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction

Zhu

Luo

Pan

et al. 2016

High Temperature Materials and Processes

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Siderite is one of the significant iron ore resources in China and yet is difficult to upgrade by traditional beneficiation processes. A process of coalbased direct reduction-magnetic separation was successfully developed for the beneficiation of siderite. However, few studies have thoroughly investigated the mechanism of the direct reduction of siderite. In order to reveal the reaction mechanism of coal-based direct reduction of siderite lump, thermodynamics of direct reduction was investigated with coal as the reductant. The thermodynamics results indicate that coal-based direct reduction process of siderite lump at 1,050°C follows the steps as FeCO 3 → Fe 3 O 4 → FeO → Fe, which is verified by chemical titration analysis, X-ray diffraction and scanning electron microscope. The microstructure of siderite sample varies with different reduction stages and some 45% porosity induced by thermal decomposition of siderite is conductive to subsequent reduction. The conversion of FeO to Fe is the main reduction rate-controlling step. The reduced product with the metallic iron size over 30 μm can be effectively beneficiated by wet magnetic separation after grinding. The obvious layered structure of reduced product is due to different heat transfer resistance, CO and CO 2 concentration.

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Studies in the thermal decomposition of natural siderites in the presence of air

Cited by 46 publications

References 8 publications

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Origins of magnetite nanocrystals in Martian meteorite ALH84001

Simultaneously Roasting and Magnetic Separation to Treat Low Grade Siderite and Hematite Ores

Reaction Mechanism of Siderite Lump in Coal-Based Direct Reduction

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