Removal of SO2 using a magnetically fluidized bed in the semi-dry flue gas desulfurization process: Roles of ferromagnetic particles and magnetic field applied

摘要

A new semidry flue gas desulfurization (FGD) process is proposed. The process uses a magnetically fluidized bed (MFB) as the reactor in which ferromagnetic particles are fluidized with simulated flue gas under the influence of an external magnetic field. A slurry of lime is continuously sprayed into the reactor by an atomizer fixed at the top of the bed. As a consequence, the desulfurization reaction and slurry drying take place simultaneously in a same reactor. Experiments with a laboratory-scale apparatus were carried out to investigate the roles of the ferromagnetic particles and the magnetic field applied in the desulfurization reaction. The results show that when ferromagnetic particles are used as the fluidization material, both sulfite (SO32-) salts and sulfate (SO42-) salts are found in the desulfurization products. When quartz particles are used, only sulfite (SO32-) salts are found. This suggests that the Fe(III) ions and Fe(II) ions result from the ferromagnetic particles dissolving in the liquid phase. In addition, the ions act as catalysts in the oxidation of S(IV) to S(VI) and react with SO2 producing FeSO3 and Fe-2(SO4)(3) as the products. On the other hand, the level of the sulfate (SO42-) salts in the products increases with increasing intensity of applied field intensity, which suggests that the oxidation of S(IV) can be enhanced by the applied magnetic field. The oxidation of S(IV) can increase the solubility of SO2, and therefore, intensify the reaction between SO2 and Ca(OH)(2), leading to an increased SO2 removal efficiency.