Process for controlling the content of divalent iron in the scrubbing solutions used to separate off SO2 and NOx

摘要

A process is described for controlling the content of divalent iron in the scrubbing solution used to separate off SO2 and NOx. The scrubbing solutions contain organic complexing agents, in particular EDTA, and calcium ions, iron ions, sulphite ions, sulphate ions and dithionate ions. It is provided that an amount of regenerated Fe2+-containing scrubbing solution is added, from a reaction vessel, to the circulated scrubbing solution such that the scrubbing solution stream conducted into the exhaust gas scrubber has a constant Fe2+ content which is between 0.9 and 1.5 g/l.