Study of the reaction mechanism for preparing powdered activated coke with SO₂ adsorption capability via one-step rapid activation method under flue gas atmosphere

In this study, the impact of different reaction times on the preparation of powdered activated carbon (PAC) using a one-step rapid activation method under flue gas atmosphere is investigated, and the underlying reaction mechanism is summarized. Results indicate that the reaction process of this method can be divided into three stages: stage Ⅰ is the rapid release of volatiles and the rapid consumption of O₂, primarily occurring within a reaction time range of 0–0.5 s; stage Ⅱ is mainly the continuous release and diffusion of volatiles, which is the carbonization and activation coupling reaction stage, and the carbonization process is the main in this stage. This stage mainly occurs at the reaction time range of 0.5–2.0 s when SL-coal is used as material, and that is 0.5–3.0 s when JJ-coal is used as material; stage Ⅲ is mainly the activation stage, during which activated components diffuse to both the surface and interior of particles. This stage mainly involves the reaction stage of CO₂ and H₂O (g) activation, and it mainly occurs at the reaction time range of 2.0–4.0 s when SL-coal is used as material, and that is 3.0–4.0 s when JJ-coal is used as material. Besides, the main function of the first two stages is to provide more diffusion channels and contact surfaces/activation sites for the diffusion and activation of the activated components in the third stage. Mastering the reaction mechanism would serve as a crucial reference and foundation for designing the structure, size of the reactor, and optimal positioning of the activator nozzle in PAC preparation.