Scrubbing water treatment process for simultaneous SO2/NOx wet scrubbing

摘要

In the simultaneous SO2/NOx wet scrubbing from flue gases, when an iron(II) complex with ethylenediaminetetraacetic acid or sodium salts thereof is used, a nitrosyl complex is formed with the NO, which is regenerated via sulphite ions. Both reactions proceed in parallel in the flue gas scrubber. At the same time, depending on the process conditions in the reduction of the nitrosyl complex, readily volatile sulphur-nitrogen compounds are also formed. Various processes are known for ejecting the dissolved reaction products from the scrubbing water which are, however, comparatively complex and laborious. It has now been found that the scrubbing water regeneration can be simplified and carried out more inexpensively in that, for regeneration, the water ejected from the scrubbing water circulation of the SO2/NOx simultaneous wet scrubbing enters into the EDTA precipitation vessel. Addition of a reducing agent, preferably sodium dithionite, completely reduces the iron(II/III) EDTA to Fe(II)-EDTA in order subsequently, by addition of sulphuric acid to a pH in the scrubbing solution of pH 0.5-3.0, to precipitate the EDTA in the scrubbing solution from the Fe(II)-EDTA complex. The resulting amounts of SO2 are returned via the pipe to the simultaneous scrubber.