Modular manganese/diatomite-Santa Barbara Amorphous-15 sorbent for moderate-temperature flue gas desulfurization

Abstract

As two typical silicon source carrier, the features of diatomite and Santa Barbara Amorphous-15 (SBA-15) supported Mn-based sorbents for moderate-temperature flue gas desulfurization are investigated in this paper. The framework structure, high mechanical strength and large density of diatomite make great contributions to the high desulfurization efficiency (96%) of diatomite supported Mn-based sorbents (MxDy). Nevertheless, the excessive Mn doping (50 wt%) exhibits the decline in desulfurization efficiency, resulting from the self-seeding nucleation and the bareness of micro-pores. Compared to M4D6, the dispersion of active component on the surface of SBA-15 is much more uniform and the sulfur capacity of SBA-15 supported Mn-based sorbent (M4S6) is sharply increased from 186 mg/g to 494 mg/g. On the other hand, the small density of SBA-15 and formation of some bare micro-regions of Mn2O3 in M4S6 lead to the weak contact between SO2 molecule and the active component on the surface of sorbent, as well as the decrease of desulfurization efficiency of M4S6 (88%). Further, the desulfurization mechanism of M4D6 and M4S6 is explored through analyzing the chemical reaction, external mass transfer and internal diffusion. The modular Mn/diatomite-SBA sorbents are developed by combining the advantages of M4D6 and M4S6. When the weight ratio of M4D6 and M4S6 reaches 3:2, the SO2 removal efficiency of modular sorbent and sulfur capacity can reach 96% and 366 mg/g, respectively.