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

A plant for the denitrification of bypass exhaust gases in the production of cement clinker, comprising:

• a rotary kiln for the sintering of raw meal to cement clinker, the rotary kiln having a rotary kiln inlet chamber,
• a calciner for the deacidification of the raw meal, the rotary kiln inlet chamber being connected directly or via a kiln riser duct to the calciner, and
• a takeoff device for drawing off the bypass exhaust gases from the region of the rotary kiln inlet chamber,
• wherein a first mixing chamber is provided for the cooling of the bypass exhaust gas, drawn off from the region of the rotary kiln inlet 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,
• wherein downstream of the first mixing chamber in the gas flow direction, a reaction section is provided which is disposed in a conduit,
• wherein the conduit has dimensioning such that the residence time of the bypass exhaust gas in the reaction section is between 0.5 s and 3 s, and
• wherein in the region of the conduit, at least one device is provided for the injection of ammonia, aqueous ammonia solution or ammonia-releasing substances into the reaction section for the denitrification of the bypass exhaust gas by the process of selective non-catalytic reduction (SNCR),
• wherein downstream of the reaction section, a second mixing chamber is disposed, for the cooling of the bypass exhaust gas to a temperature of between 150° C. and 250° C. to remove chloride compounds from the gaseous phase by deposition, and
• wherein downstream of the second mixing chamber at least one filter is disposed for the dedusting of the bypass exhaust gas.