Abstract
The rate of reaction of carbonyl sulfide with metallic iron was studied by measuring the ratt of sulfurization of sponge iron pellets in COS-CO gas mixtures at temperatures from 800°C to 1000°C. The sponge iron pellets had been produced by hydrogen reduction of hematite pellets.
The results obtained are as follows:
1) The product shell layers were proved to be nonstoichiometric ferrous sulfide having the atomic ratio of S/Fe=1.06.
2) Negligible amount of carbon was deposited on the pellets in the stream of 5% COS-CO gas mixture.
3) The sulfurization reaction was analyzed on the basis of the unreacted-core model and it was found that the reaction was controlled by the following three steps; the gas-film mass transfer, the intraparticle gaseous diffusion, and the chemical reaction at the sulfide-iron interface.
4) The chemical reaction rate constant kγ and the effective intraparticle diffusion coefficient De are expressed respectively by the following Arrhenius type equations:
log kγ= 3.053-13400/2.3 RT
log De= 4.746-30430/2.3 RT
It is noteworthy that temperature coefficient of De is fairly greater than that of kγ, which results in the predominant contribution of chemical resistance to the over-all resistance even in higher temperatures.
