Multi-stage simultaneous SO2 separation and NOx separation preferably downstream of power stations having different pHs in the scrubbing stages

摘要

In the main application P3414152.9, a process is described for separating out nitrogen oxides when a simultaneous SO2 load is present, in which the scrubbing process using additives for the elimination of SO2 and NOx is carried out in such a way that it is operated in a two- or multi-stage manner, fundamentally the scrubbing stage being simultaneously an SO2 and NOx separation respectively provided downstream of an acidic scrubbing stage. In order further to improve the process according to the main application, according to the invention it is proposed that in the first scrubbing stage (2), the scrubbing liquid is circulated having a pH between pH 3 and pH 4 via an iron reactor (3) and in the subsequent second scrubber part, the circulating liquid has a pH above 5. Sodium dithionite or an equivalent reducing agent is added to the scrubbing circulation of the scrubbing stage (4) as an inoculant, in order to keep the iron II chelate above the required redox potential in both scrubbing stages (3) and (4). IMAGE