DESULFURIZATION OF HOT COAL-DERIVED FUEL GASES WITH MANGANESE-BASED REGENERABLE SORBENTS .2. REGENERATION AND MULTICYCLE TESTS

In a previous paper, the reduction and sulfidation thermodynamic and kinetic characteristics of four manganese-based high-temperature desulfurization sorbents were investigated. A formulation, FORM4-A, which consisted of manganese carbonate, alundum, and bentonite exhibited the best combination of capacity and reactivity; whereas, FORM1-A, which consisted of Mn ore, alundum, and dextrin exhibited the best combination of strength, capacity, and reactivity. In this paper the thermodynamic feasibility of regeneration is discussed. The kinetics of regeneration of sulfided (loaded) pellets with air is studied in the 800-1000 degrees C temperature range. Repeated cycling of the leading sorbent formulation (FORM4-A) was then conducted in a thermogravimetric apparatus (TGA), up to five consecutive cycles. One important finding was that the capacity of the pellets for sulfur pickup from fuel gas and the kinetics of reduction, sulfidation, and regeneration improved with recycling without compromising the strength. This appears to be a result of radial microcrack formation which reduced the solid-state diffusion path within the pellet.