Von Roll Ag

Rene Vock

Hans Ruegg

For reducing nitrogen oxides in the flue gases of a firing plant, fresh ammonia water, i.e. an aqueous solution of ammonia (NH.sub.3), is introduced into the flue gas flow. For achieving a high degree of separation of the nitrogen oxide a superstoichiometric addition of ammonia (NH.sub.3) is necessary. Most of the excess ammonia is washed out in the wet washer (6). A liquor, e.g. milk of lime (Ca(OH).sub.2), is dosed into the wash water in a connecting line (10) to a stripping column (11), so that a pH-value above 9.5 is obtained. The now physically dissolved ammonia (NH.sub.3) is desorbed from the wash water in the stripping column (11). The steam/ammonia mixture passing out of the stripping column (11) is condensed in a condenser (17) and the condensate in the form of ammonia water is admixed to the fresh ammonia water in feed line (3). As a function of the nitrogen oxide reduction, approximately 10 to 50% of the fresh ammonia water can be saved.

Process for the recovery of ammonia from flue gases

Nitric oxides are removed from flue gases by the spraying-in of a liquid containing a reducing agent. The atomizing agent necessary for forming the liquid into individual droplets and for the transportation of the droplets is introduced together into the central feed pipe for the liquid before it is branched to the individual spray points.

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Bonstetten, Switzerland

Rene Vock