抄録
The Mitsui SO2 and NOx removal wet process embodies ideal features for a process to clean up SO2 and NOx emissions by absorption of them in aqueous solution of FeII. EDTA.
This process consists of four steps: (1) Scrubbing of SO2 and NOx in flue gas at 40-60°C: FeII·EDTA+NOx→FeII NO·EDTA, FeII·EDTA+O2-4FeIII·EDTA, FeIII·EDTA+SO2→FeIII·SO2·EDTA.(2) Electrolytic reduction of FeIII·EDTA to FeII·EDTA at 40-100°C: FeIIIEDTA+e→FeII·EDTA.(3) Stripping of SO2 and NO by heating the solution to 100-110°C: FeII·NO·EDTA→FeII·EDTA+NO (g), FeII·SO2·EDTA→FeII·EDTA+SO2 (g) (4) Gasphase catalytic oxidation at 400-500°C forming SO3: SO2+NO→SO3+N2.
The regeneration of the solution absorbed SO2 and NO is accomplished by elec-trolytic reduction and stripping. The regenerated FeII·EDTA solution is recycled to a absorber. The conc. sulfuric acid is recovered from SO3 gas.
The electrolytic reduction step can be replaced by modified Claus reaction of H2S with SO2 and FeIII·EDTA. The elemental sulfur is recovered in this reaction.
