Sulfur Chemistry and Its Role in Corrosion and Deposits

Abstract

Sulfur in fuel oil and coal, and its resultant oxidation to SO3 during combustion, is a recognized factor in corrosion and deposits. As a step toward controlling the formation of SO3 , and eventually controlling the conditions and rate of corrosion, a program has been undertaken under ASME support to establish, among other things, the mechanism by which sulfur compounds are oxidized to SO2 and to SO3 in flames. The present paper reviews some of the basic thermodynamics and reaction kinetics pertaining to the oxidation of H2 S and SO2 , and to the SO2 –SO3 equilibrium. Included in the review are discussions of the stability of H2 S, the slow oxidation of sulfur vapor and of H2 S, the induction period (preignition) reactions leading to the fast, explosive oxidation of H2 S, and effects of additives on the explosion reaction. The heterogeneous (catalyzed) oxidation of SO2 is discussed in terms of the effects of specific catalysts on the SO2 –SO3 equilibrium.