Method and plant for denitrifying bypass gases in a multi-stage system of mixing chambers in a plant for producing cement clinker

A method for the denitrification of bypass exhaust gases in a plant for producing cement clinker, wherein

• the plant has a rotary kiln for the sintering of raw meal to cement clinker, and has a calciner for the deacidification of the raw meal, downstream of the rotary kiln in the kiln exhaust gas flow direction,
• the rotary kiln has a rotary kiln inlet chamber which is connected directly or via a kiln riser duct to the calciner, and
• the bypass exhaust gas is drawn off in the region of the rotary kiln inlet chamber, comprising the steps:
• passing of the bypass exhaust gas into a first mixing chamber, where
• the bypass exhaust gas is cooled in the first mixing chamber to a temperature of between 800° C. and 950° C. so that chloride compounds remain in a gaseous phase after the bypass exhaust gas is cooled,
• passing of the bypass exhaust gas from the first mixing chamber through a reaction section disposed in a conduit, where
• the residence time of the bypass exhaust gas in the reaction section is between 0.5 s and 3 s, and where
• ammonia, aqueous ammonia solution or ammonia-releasing substances are injected into the reaction section for the denitrification of the bypass exhaust gas by the process of selective non-catalytic reduction (SNCR),
• passing of the bypass exhaust gas from the reaction section into a second mixing chamber, where
• the bypass exhaust gas is cooled in the second mixing chamber to a temperature of between 150° C. and 250° C. to remove chloride compounds from the gaseous phase by deposition, and by
• passing of the bypass exhaust gas from the second mixing chamber to at least one filter for the dedusting of the bypass exhaust gas.