Process for preparing hydroxylamine from NO.sub.x -containing flue gases

A process for preparing hydroxylamine from NO.sub.x -containing flue gases by nitrogen removal from the flue gases combined with hydroxylamine synthesis by catalytic reduction of NO with hydrogen, comprising the steps of:

• (a) inserting a NO.sub.x -containing flue gas into the bottom section of an absorber, inserting an aqueous FeII-EDTA solution into the head section of the absorber, absorbing the NO.sub.x contained in the flue gas at a comparatively low temperature by countercurrent contact of the flue gas with the aqueous FeII-EDTA solution to form a FeII(NO)-EDTA complex dissolved in the aqueous solution, removing the complex together with the aqueous solution from the absorber as bottom product, inserting the complex and the aqueous solution into a desorber as head product via a heat exchanger to increase the temperature thereof, and removing the flue gas freed of NO.sub.x overhead from the absorber,
• (b) inserting water vapor and hydrogen into the bottom section of said desorber, and desorbing NO from the aqueous solution of the FeII(NO)-EDTA complex by countercurrent contact with the water vapor and with the hydrogen to form a solution containing dissolved FeII-EDTA complex, removing the solution containing dissolved FeII-EDTA complex from the desorber as bottom product and feeding the bottom product back into the upper section of the absorber via an electrolyzer for reducing FeIII-EDTA to FeII-EDTA and via a heat exchanger and a cooler for step-by-step lowering of the temperature of the bottom product, and
• (c) removing overhead from the desorber a gaseous NO, H.sub.2 and water vapor mixture, removing water vapor from the mixture in a condenser and returning the water vapor to the reboiler, and leading the gaseous mixture of NO and hydrogen to direct catalytic hydroxylamine synthesis by catalytic reduction of the NO with hydrogen.