Scrubbing out SO2 and NOx from exhaust gases downstream of combustion plants

摘要

The invention relates to a process for scrubbing SO2 and NOx from exhaust gases downstream of combustion plants and represents an application additional to Patent Application P 3419611.0. In order to achieve a high separation out of NOx, in particular in the case of exhaust gases downstream of combustion plants which have a relatively small SO2/NOx molar ratio of 2 : 1, according to the invention it is proposed that the first scrubbing stage has the task of separating out the SO2 and does not comprise the main feature of simultaneous separation out of NOx, and that the main feature in the second scrubbing stage is the separation out of NOx, in which second scrubbing stage SO2 is still unavoidably scrubbed out to a certain extent, both scrubbing stages operating with separate scrubbing liquid circulations and the first scrubbing liquid circulation being operated using carboxylic acid without polycarboxylic acid (EDTA) and in the second scrubbing stage polycarboxylic acid (EDTA) or diphosphonic acids which contain divalent iron complex being added, with simultaneous addition of oxygen-binding substances, such as salts of sulphurous acid, and/or reducing agents such as ascorbic acid.