Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.352700
Title: Reduction and carburisation of iron ore in a fluidised bed
Author: Hutchings, K. M.
Awarding Body: University of Sussex
Current Institution: University of Sussex
Date of Award: 1984
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Abstract:
The literature on the following subjects has been reviewed: the reduction of iron oxides with methane, carburisation of iron with methane, the reduction of iron ore with hydrogen and carbon monoxide and the factors affecting the rates of gas-solid reactions in fluidised beds. The rates of reduction and carburisation of granular hematite ore (±180-250 . im particles), fluidised by the reducing-carburising gas in a quartz reactor, and measured over the temperature range 900-1100K by analysis of the outlet gas using gas chromatography, are reported. The reactions of pure hydrogen, some H2-H20 mixtures, and various HZ-(ßi4 mixtures are covered. Also surface areas of iron and partially reduced oxide, measured by nitrogen i joýmariý'ý cn adsorption, and,, solid structures, studied by optical and electron microscopy are presented. Established models of reactions in fluidised beds have been adapted to give tentative rate constants for the reduction of wustite to iron at 900K. The maximum values are similar to those derived in other work using completely different techniques. Rate constants have also been obtained for the reduction of magnetite to wustite using H2-H2O and 00-OD at 973K; these have not been well established previously. The variation of the rate constants with degree of reduction is discussed with reference to the surface area of the solid and the formation of non-porous product layers. In the reaction of H2-C[ mixtures with hematite between 900 and 1100K the methane is unreactive until iron is formed (approx. 40% reduction); it then begins to decompose catalytically and the reduction rate increases. Carbon deposition does not occur until 50-70% reduction. At 900K there is some indication from the reduction rate and the electron micrographs that carbon blocks pores and hinders the final stages of reduction. The initial rates of carburisation per gram of iron are similar to those obtained in previous work using pellets over the range of mixtures studied. At lower temperatures there is an increased tendency for the rate of carburisation to drop with increasing degree of carburisation of the iron, this is accentuated by high gas flowrates and high carbon potentials in the gas. Because of the insensitivity of the rate to the iron surface area and gas composition, the decomposition of methane is not thought to be rate determining. The rates of methane decomposition, iron oxide reduction, and carburisation are discussed with reference to the catalytic activity of iron as it forms fron the oxide and is then contaminated with carbon and carbides, cacd, týo the gas composition and gas dynamics in the bed. At 1000 and 1100K fluidisation collapses temporarily as iron forms, but with further reduction and carburisation re-fluidisation occurs, presumably because carburisation weakens the adhesion of the iron particles.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.352700  DOI: Not available
Keywords: Chemical engineering Chemical engineering
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