SO3 removal characteristics from flue gas of FCC regeneration process by activated carbon modified red mud adsorbent

Sulfur trioxide (SO3) is one of the major air pollutants in the flue gas of Fluid catalytic cracking (FCC) units during the regeneration process in refineries. However, it is difficult to remove SO3 with the existing desulfurization systems. Nowadays, alkaline adsorbent spraying technology has been a promising method to remove SO3. However, there is no relevant application research in the field of FCC regeneration flue gas. Therefore, in this paper, The SO3 removal characteristics from FCC flue gas by activated carbon modified red mud adsorbent were studied, including modification method, reaction temperature and flue gas components. Combined with characterization analysis of adsorbents, the mechanism of SO3 removal was studied. It was found that when the AC mass ratio is 10% and modification temperature is 400 ℃, the best LBRMAC adsorbent was achieved. When particle size is 0.096–0.125 mm and reaction temperature is 400 ℃, the highest SO3 adsorption efficiency is up to 83.4%. The addition of NO has little influence on the adsorption efficiency of SO3. The addition of SO2 leads to competitive adsorption between SO3 and SO2, resulting in a rapid decline in the removal efficiency of SO3. Meanwhile, the characterization analysis proves that the SO3 adsorption process mainly include chemical kinetics control stage and product layer diffusion stage.