Reactivity of Iron Oxide Sorbents for Hydrogen Sulfide Removal from Hot Syngas

摘要

Reactivity of an iron oxide pellet containing 45 wt % Fe sub 2 O sub 3 with a hot gas containing H sub 2 S, CO and H sub 2 was studied in a thermogravimetric analyzer (TGA) at temperatures between 600 to 900 exp 0 C. During the first period of the reaction, both the sulfurization (reaction with H sub 2 S) and the reduction (reaction with H sub 2 and CO) take place simultaneously. Spongy metal iron formed as the result of the rapid reduction reaction is much more reactive with H sub 2 S than the iron oxide itself. Therefore, reactivity studies were conducted for reduction (using iron oxide pellet) and for sulfurization (using completely reduced pellet) separately. The reduction experiment resulted in the following findings: (1) for sample pellets of size smaller than 0.2 mm, the chemical reaction rate controls the reduction rate. The activation energy obtained from the Arrehnius plot is 12.3 kcal/mol, (2) the effect of diffusion on the reduction rate becomes increasingly important as the pellet size increases beyond 0.2 mm. For the sample pellet of 6.4 mm in diameter, the rate is dominated by the diffusion rate. From the results of the sulfurization experiment, it has been observed that the reaction is approximately first order with respect to H sub 2 S and that the final sulfurized iron has the composition range between FeS sub 1 . sub 1 to FeS sub 1 . sub 2 . The sulfurization reaction rate observed showed nearly the same trends as that in the reduction rate as indicated in (1) and (2) above. The activation energy obtained for the sulfurization is 2.65 kcal/mol. 3 references, 35 figures. (ERA citation 10:006256)