Process for the simultaneous removal of sulphur oxides and nitrogen oxides from combustion exhaust gases in an ammonia scrubber

摘要

The removal of sulphur oxides and nitrogen oxides by ammonia is only incompletely solved because of the ammonia slip and hitherto has taken place in separate processes. Insufficient nitrogen oxide solubility has made complex oxidation processes necessary. The circulating alkali solution for SO2 absorption and oxidation permits the integration of the nitrogen oxide removal after which nitrogen monoxide is partially oxidised in a connected reactor to increase the nitrogen oxide solubility. In the scrubbing liquor the reaction NO + NO2 + 2NH3 + H2O = 2NH4NO2 then takes place. The ammonium nitrite is decomposed in the heat without residue. The ammonia slip is reduced by cooling the scrubbing liquor and scrubbing the clean gas with acidic flue gas condensate. The circulatory scrubbing process permits absorption even in the event of plant fluctuations and does not require complete oxidation and decomposition. Not having high control system expenditure and complex oxidation apparatus, the process is also suitable for small-scale plants.