Evolution of pore structure of Ca-based sorbent in simultaneous removal of SO₂ and NO_x

The pore structure of the sorbent plays a significant role in gas-solid surface reaction under low temperature and humid conditions. By using the nitrogen adsorption method, the pore structure of Ca(OH)₂ particles subjected to SO₂ and NO₂ for different reaction times were analyzed. The evolution mechanism of the absorbent surface structure was discussed in combination with the absorption mechanisms of SO₂ and NO₂ on the surface of Ca(OH)₂ particle. The results show that the presence of the surface reactions products changes the pore shape, but has a negligible effect on the BET surface area and pore volume. The amount of the pores <7 nm and >30 nm decrease with the increase of reaction time, while the pores from 7 nm to 30 nm show an opposite trend. The presence of the pores (7 nm<d<30 nm) can not only account for the unchanged of BET surface area and pore volume during reactions, but also affect the fractal characteristics of the absorbent. The expansion and depositing of the reaction products result in the shrinking of the pores, and the change of pore shape structure.