Evaluation of Mn-based sorbent for flue gas desulfurization through isothermal chemical-looping system

Abstract

An energy-saving isothermal chemical-looping system was proposed to remove SO2 from flue gas choosing manganese oxide as the active component. To investigate the effect of pore structure on the desulfurization performance, desulfurizers were prepared via the sol-gel method with 60 wt% silicon carbide, diatomite and zeolite molecular sieves as the support material. Mn4Z6 had the largest specific surface area but lower desulfurization efficiency, resulting from the blocking and collapse of original channel in the desulfurization process. Mn4D6 exhibited the highest SO2 removal efficiency, benefiting from the nanoscale oval crystalline phases, staggered micropores and stable frame structure. A better desulfurization performance with the sulfur capacity of 186 mg-SO2/g-sorbent was obtained by operating at 620 °C with the SO2 concentration of 800 ppm and space velocity of 7500 h−1. After five desulfurization-regeneration cycles, 72% of the initial sulfur capacity was retained, revealing the high durability of Mn4D6. The hazardous flue gas was purified in the desulfurization process and valuable pure SO2 and elemental sulfur could be recycled in the regeneration process. Furthermore, the mechanism of desulfurization-regeneration cycle was elaborated for the first time. Present investigation suggested that Mn4D6 operated at the isothermal chemical-looping system can be a potential candidate for flue gas desulfurization and recycling high value-added byproducts.