Mechanism and kinetics of high-temperature flue gas desulfurization with magnesia tailings as a desulfurization sorbent

High-temperature flue gas desulfurization using magnesite tailings as a sorbent has economic and environmental benefits. In order to assess the feasibility, the reaction mechanism and kinetic characteristics of high-temperature flue gas desulfurization using magnesite tailings as the sorbent were studied via a micro fluidized bed reaction analyzer (MFBRA). The dynamics of magnesite calcination and sulfation, and the evolution of the inner pore structure of magnesite particles were studied. The results show that the reaction process includes a calcination reaction of magnesite to MgO, and a sulfation reaction between MgO and SO2 to form MgSO4. The calcination reaction rate is faster than the sulfation reaction. Decomposition of magnesite is fast at beginning that resulted in quick increase of MgO and also the sulfation reaction between MgO and SO2. The amount of nascent MgO consumed by the sulfation reaction is low and the available MgO is excessive. After that period the sulfation reaction rate increases, thereby the formation of MgSO4 increases accordingly. The increased MgSO4 covers MgO surface that leads to a reduction of sulfation rate. The calcination rate of MgCO3 reduces in the later stage and the internal pore formation slows down with dense MgSO4 layer covers small pores. Consequently, the sulfation reaction rate tends to be controlled by the diffusion through the MgSO4 layer, leaving some MgCO3 and MgO unreacted at the end of the operation. © 2023 Zhejiang University. All rights reserved.