923 KのCO-H<SUB>2</SUB>-H<SUB>2</SUB>S系ガス中での鉄表面上の炭素析出

Abstract

The behavior of carbon deposition on iron in CO-H2-H2S mixtures containing small amounts of H2S gas in the range without the formation of FeS has beem studied by means of metallography and thermogravimetry. Kinetic measurements show that carbon deposition is retarded or accelerated depending upon the ratio of partial pressure of H2S to H2, PH2S⁄PH2. Particularly in 20%CO-H2-H2S mixtures, at PH2S⁄PH2=0∼2×10−6, the rate of carbon deposition increases with the increase in the ratio of partial pressures because of the acceleration of filamentous carbon deposition, while at PH2S⁄PH2≥5×10−6, the film of Fe3C forms on the substrate, so that carbon deposition is retarded. And it is found in the middle range of these ratios that the rate initially decreases but significantly increases later. This carbon deposition behavior may be ascribed to the acceleration or the retardation of formation and decomposition of Fe3C as well as the depression of laminar carbon deposition by the action of absorbed sulfur on the iron surface through the dissociation reaction of H2S gas. In particular, small amounts of sulfur may accelerate the decomposition of Fe3C and promote the deposition of filamentous carbon by the following reaction that removes atomic hydrogen, i.e. a Fe3C stabilizing element.(This article is not displayable. Please see full text pdf.)