Initial step of flue gas desulfurization - An IR study of the reaction of SO2 with NOx on CaO-

Flue gas desulfurization contributes much to the prevention of acid lain. i n a dry-type flue gas desulfurization, promotive effect of NO on SO2 absorp tion is observed. To elucidate the reaction mechanisms far absorption of SO 2 by a calcium compound in a dry-type flue gas desulfurization, the states of adsorbed SO2, NO, and NO2 on CaO and the reactivity of the adsorbed SO2 with NO, NO2, and O-2 were studied by IR and temperature-programmed desorpt ion (TPD). Sulfur dioxide (SO2) and NO2 were adsorbed on CaO mainly in the form of sulfite ion (SO32-) and nitrate (NO3) complex, respectively. Nitrog en oxide (NO) is adsorbed in the forms of nitrito (NO2) complexes, free nit ro, and nitro or chelating nitro complexes. The sulfite ion reacts with the adsorbed species of NO to be oxidized to sulfate ion (SO42_) but reacts ne ither with the nitrate complex nor with O-2 The nitrito complexes, free nit ro, and nitro or chelating nitro complexes act as an oxidizing agent toward sulfite ion on CaO to form sulfate ion. The transformation of SO32- ion in to SO42- ion by NO is further accelerated in the presence of O-2.