Process for removing HCl, HF, SO3, SO2 and NOx from combustion exhaust gases by simultaneous wet scrubbing with controlled scrubbing water circulation and specific addition of lime

摘要

In the main application P3525051.8, it is proposed to remove SO2 and NOx from combustion exhaust gases by using a wet circulation scrubbing, the scrubbing water of which contains iron (II) EDTA complex or iron (II) NTA complex. To keep the iron (II) complex within the scrubbing solution, reducing agents are added or scrubbing water treatments are carried out in the bypass in order to reduce again the iron oxidised in the chelate complex by atmospheric oxygen from iron (II) to iron (III) and thus to minimise the use of expensive reducing agents. In order further to improve the process according to the main application, in particular with regard to decreasing the consumption of reducing agent, according to the invention it is proposed that hydrated lime or limestone (5) is added into the suction line of the scrubbing water circulation (6). The amount of lime addition is stoichiometrically controlled in accordance with the flue gas pollutant rate. A portion of water from the main scrubbing water circulation is fed via a line (7) to a gravity separator (13) to separate out solids. The part-stream water volume freed from solids is returned to the scrubber sump. The solids (approximately 30%) thickened in the gravity separator (13) are dewatered via a dewatering station (9),... Original abstract incomplete. IMAGE