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 r egenerable sorbents capable of removing hydrogen sulfide from hot coal -derived fuel gases. Manganese ore as well as manganese carbonate, pre cipitated from aqueous solutions, combined with alumina to form indura ted pellets is shown to hold promise of being a highly-effective, inex pensive, regenerable sulfur sorbent for hot fuel gases. Although the t hermodynamics for sulfur removal by manganese predicts somewhat higher hydrogen sulfide overpressures than can be accomplished with zinc-bas ed 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 l imits the temperatures to which desulfurization can be effectively acc omplished 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 fa bricated from manganese and alumina, establishes the thermodynamic fea sibility of hydrogen sulfide removal from hot simulated coal gases usi ng these sorbents, and presents an analysis of the sulfidation reactio n kinetics based on thermogravimetric experimental results.