In recent studies, the thermodynamic feasibility of using manganese-based sorbent pellets for the removal of H2S from hot coal-derived fuel gases, and the subsequent regeneration of loaded (sulfided) pellets with air was established. Screening sulfidation tests on a number of formulations, consisting of a manganese-containing compound (ore or MnCO3), alundum (Al2O3), and organic or inorganic binders, were carried out using H2S-H-2 gas mixtures in a thermogravimetric apparatus (TGA) at temperatures ranging from 700-1000 degrees C. A formulation, designated FORM4-A, was found to possess the best combination of sulfur capacity, reactivity, and strength. Regeneration tests determined that for T greater than or equal to 900 degrees C, loaded pellets can be fully regenerated with air in 10-15 min, without sulfate formation. This paper reports on fixed-bed testing of the leading Mn-based sorbent pellet formulation (i.e., FORM4-A). Experiments are carried out to test the long-term durability and regenerability of the sorbent using a simulated Tampella-U fuel gas for sulfidation and air for regeneration. In addition, the effect of temperature on sulfidation reaction equilibrium is determined in the range 800-1000 degrees C. A reassessment of the equilibrium states of reactions involving solid MnO, MnS, Mn(3)O4, and MnSO4 is then presented based on the results obtained and a recent study by Turkdogan.