Investigation of gas-solid reaction kinetics in iron compounds

Technical Report · Wed Jan 01 00:00:00 EST 1986

OSTI ID:5752205

Coombs, P G

Studied were the hydrogen reduction of FeO, the cyclic reduction and oxidation of Fe/sub 2/O/sub 3/ using hydrogen and dry air as the reacting gases, and the oxidation of FeS in dry flowing air. The decomposition of Fe/sub 2/(SO/sub 4/)/sub 3/ in air and the oxidation of iron reduced from FeO were also investigated. The direct hydrogen reduction of FeO and Fe/sub 2/O/sub 3/ powder between 723 and 873/sup 0/K led to sigmoid-shaped curves on which a zero-order kinetic expression was employed. A critical temperature effect was observed at 803/sup 0/K for the reduction of FeO. Activation energies of 58 and 51 kJ/mol were calculated for the low and high temperature reduction of FeO. A similar value of 53 +- 4 kJ/mol was derived for Fe/sub 2/O/sub 3/ reduction. Cycling was found to reduce the rates of both the reduction and oxidation reactions in Fe/sub 2/O/sub 3/. The oxidation of FeS is complex. A model is proposed, and the various observations are discussed in terms of a sequence of solid-state and gas-solid reactions. The oxidation of stoichiometric FeS (troilite) between 648 and 923/sup 0/K led to a final product of Fe/sub 2/O/sub 3/ as well as a variety of intermediate compounds which included Fe/sub 1-x/S (pyrrhotite), FeS/sub 2/ (pyrite), Fe/sub 2/(SO/sub 4/)/sub 3/, and Fe/sub 3/O/sub 4/ (magnetite). Oxidation kinetics at intermediate temperatures were controlled by the Fe/sub 2/(SO/sub 4/)/sub 3/ formation and decomposition. The activation energies for FeS oxidation and Fe/sub 2/(SO/sub 4/)/sub 3/ decomposition are 192 kJ/mol and 219 kJ/mol.

• Research Organization: California Univ., Davis (USA)
• DOE Contract Number: AS03-80ER10708
• OSTI ID: 5752205
• Report Number(s): DOE/ER/10708-T5; ON: DE86012296
• Resource Relation: Other Information: Portions of this document are illegible in microfiche products. Thesis
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
IRON
OXIDATION
IRON OXIDES
REDUCTION
IRON SULFATES
DECOMPOSITION
IRON SULFIDES
AIR
CHEMICAL REACTION KINETICS
HIGH TEMPERATURE
HYDROGEN
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
FLUIDS
GASES
IRON COMPOUNDS
KINETICS
METALS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
SULFATES
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
360105 - Metals & Alloys- Corrosion & Erosion