| The focus of much current work being performed by the Morgantown Energy Technology Center (METC) of the Department of Energy on hot coal-derived fuel gas desulfurization is in the use of zinc-based sorbents. Extensive research, however, casts doubt that these sorbents can be utilized even for the mild conditions associated with fixed-bed operation. Accordingly, METC has shown interest in formulating and testing manganese-based pellets as alternative effective sulfur sorbents.; To substantiate the potential superiority of Mn-based pellets, a systematic approach toward the evaluation of the desulfurizing power of single-metal sorbents is developed based on thermodynamic considerations. Then, the feasibility of using Mn- based sorbents for the removal of H{dollar}sb2{dollar}S from hot coal-derived fuel gases, and the subsequent regeneration of loaded sorbents was established.; A novel process is developed for the manufacture of Mn-based spherical pellets which have the desired characteristics required during the long-term use in a high-temperature desulfurization operation. Screening sulfidation tests on a number of formulations were carried out using H{dollar}sb2{dollar}S-H{dollar}sb2{dollar} gas mixtures in a thermogravimetric apparatus (TGA) at temperatures ranging from 700 to 1000{dollar}spcirc{dollar}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 {dollar}geq{dollar} 900{dollar}spcirc{dollar}C, loaded pellets can be fully regenerated with air in 10 to 15 minutes. Repeated cycling of FORM4-A pellets was then conducted. One important finding was that the pellet sulfur capacity and the kinetics of reduction, sulfidation, and regeneration reactions improved with recycling without compromising the strength.; Testing of FORM4-A pellet formulation was carried out in a 2-inch fixed-bed reactor using a Tampella-U fuel gas for sulfidation and air for regeneration. These tests also showed improvement in capacity and kinetics with the sulfur capacity being about 22% by weight of the original pellet, which corresponds to approximately 90% bed reactor using a Tampella-U fuel gas for sulfidation and air for regeneration. These tests also showed improvement in capacity and kinetics with the sulfur capacity being about 22% by weight of the original pellet, which corresponds to approximately 90% bed utilization.; Kinetic analysis of TGA experimental data, based on the shrinking unreacted-core model, determined that beyond approximately 35% reaction completion, sulfidation and regeneration reaction rates were controlled primarily by gaseous counter-diffusion through the porous product layer. |
