Growth mechanism of product layer in SO_2 and NO_x simultaneous removal by calcium-based sorbent

In order to analyze the growth mechanism of product layer in SO2 and NOx removal by calcium-based sorbent, the single-crystal Ca(OH)2(0001) surface was used to simulate the pore wall and external surface of the sorbent. The growth of product layer was analyzed under different reaction environments. The growth mechanism of product layer in SO2 and NOx simultaneous removal by calcium-based sorbent was proposed, combining crystal growth theory and discrepancy between SO2 and NOx single removal. SO2 removal reaction firstly occurred in the local area of the single-crystal surface to result in expansion of surface and formation of convex structure. Subsequently, the reaction and expansion area gradually extended, which led to formation of the continuous dense product layer. Due to solubility and diffusion of NO2 removal product in the water film, NO2 reaction had an obvious etching effect on the sorbent surface. When SO2 removal reaction coexisted with NO2 removal reaction, the etching action of NO2 removal reaction could inhibit formation of the continuous dense SO2 removal product layer. Meanwhile, the presence of NO2 removal product could change the growth habit of the SO2 removal product. Therefore, the sorbent surface structure after simultaneously reacting with SO2 and NOx was loose.