Reducing agent stockage for the scrubbing solution for the simultaneous scrubbing of SO2 and NOx

摘要

In order to avoid too high an EDTA consumption in the scrubbing solution, according to the invention it is proposed that it is composed of an EDTA or NTA solution, the EDTA being mixed with water and an alkali metal hydroxide solution, preferably sodium hydroxide solution, and containing an iron II masking agent to prevent the oxidation of iron II to iron III and an addition of reducing agents to reduce iron III to iron II at a pH of the scrubbing solution of above 5 and less than 8. The scrubbing solution is advantageously made up with a sodium sulphate content of above 20 g per litre and a sodium sulphite content of above 10 g per litre. The iron II masking agent used in the scrubbing solution is a carboxylic acid, preferably tartaric acid, and the reducing agent used in the scrubbing solution is sodium dithionite.