DESULFURIZATION OF HOT COAL-DERIVED FUEL GASES WITH MANGANESE-BASED REGENERABLE SORBENTS .1. LOADING (SULFIDATION) TESTS

In earlier studies, zinc ferrite and zinc titanate were developed as regenerable sorbents capable of removing hydrogen sulfide from hot coal-derived fuel gases. Manganese ore as well as manganese carbonate, precipitated from aqueous solutions, combined with alumina to form indurated pellets is shown to hold promise of being a highly-effective, inexpensive, regenerable sulfur sorbent for hot fuel gases. Although the thermodynamics for sulfur removal by manganese predicts somewhat higher hydrogen sulfide overpressures than can be accomplished with zinc-based sorbents, zinc tends to be reduced to the metallic state under coal gasification conditions resulting in loss of capacity and activity by volatilization of reactive surfaces. This volatilization phenomenon limits the temperatures to which desulfurization can be effectively accomplished to less than 550 degrees C for zinc ferrite and 700 degrees C for zinc titanate, whereas, manganese-based sorbents can be utilized at temperatures well in excess of 700 degrees C. This paper addresses the physical and chemical behavior of several sorbent formulations fabricated from manganese and alumina, establishes the thermodynamic feasibility of hydrogen sulfide removal from hot simulated coal gases using these sorbents, and presents an analysis of the sulfidation reaction kinetics based on thermogravimetric experimental results.