Abstract: NO.sub.x is removed from flue gases by contacting same in the presence of active coke/active carbon and a reducing agent, e.g. NH.sub.3, CO or H.sub.2. According to the invention, the adsorbent is precharged with the reducing agent, thereby increasing the surface area over which the adsorbent can react with the flue gas and decreasing the levels of gas-reducing agent which must be used and which may appear in the cleaned gas.

Abstract: A flue gas stream having passed a flue gas desulfurization plant 2 enters a reactor 6 flowing through an activated carbon bed. The flue gas entering the reactor continuously is discontinuously blended with ammonia, thereby achieving a low ammonia content of the flue gas leaving the reactor, while maintaining a high efficiency of nitrogen oxide removal. The duration of ammonia addition and the rate of flow at which ammonia is added to the flue gas stream are controlled as a function of the desired efficiency of nitrogen oxide removal and the ammonia concentration measured in the reactor.