Installation for producing cement clinker, and method for operating one such installation

An installation for manufacturing cement clinker from raw meal which is treated thermally in a combustion process by preheating, calcining, sintering and cooling stages, comprising:

• an exhaust gas stream of the sintering stage and an exhaust gas stream of the cooling stage in the calcining stage which is supplied with fuel being arranged and directed to calcine the raw meal,
• a calcining combustion chamber having an upper raw-meal-free reducing zone with a feed for secondary fuel arranged at the upper side of the combustion chamber, a first tertiary partial airstream with sub-stoichiometric fuel combustion being integrated in the calcining stage in order to form a CO-containing reduction zone to reduce a pollutant NOx and to gasify the secondary fuel, and an underside of the combustion chamber being connected via a connecting line to a lower region of a rotary kiln exhaust gas rising line,
• the combustion chamber having a lower zone, an inflow of at least one raw meal partial stream and of a second tertiary partial air stream being arranged in a junction region between the upper raw-meal-free, reducing zone and the lower zone,
• a height of the upper, raw-meal-free zone of the combustion chamber in relation to a height of the lower zone having a ratio of 5:1 to 1:1,
• a third tertiary partial airstream line and a second raw meal partial stream passing into the rotary kiln exhaust gas rising line above a junction of a combustion chamber connecting line and the rotary kiln exhaust gas rising line in the upper region of the combustion chamber, and
• each of the three tertiary partial airstream lines is assigned an actuating element for regulating a respective tertiary air flow rate.

A method for operating an installation for manufacturing cement clinker from raw meal which is treated thermally in a combustion process by preheating, calcining, sintering and cooling stages, with an exhaust gas stream of the sintering stage and an exhaust gas stream of the cooling stage in the calcining stage which is supplied with fuel being arranged and directed to calcine the raw meal, a calcining combustion chamber having an upper raw-meal-free reducing zone with a feed for secondary fuel arranged at the upper side of the combustion chamber, a first tertiary partial airstream with sub-stoichiometric fuel combustion being integrated in the calcining stage in order to form a CO-containing reduction zone to reduce a pollutant NOx and to gasify the secondary fuel, and an underside of the combustion chamber being connected via a connecting line to a lower region of a rotary kiln exhaust gas rising line, the combustion chamber having a lower zone, an inflow of at least one raw meal partial stream and of a second tertiary partial air stream being arranged in a junction region between the upper raw-meal-free, reducing zone and the lower zone, a height of the upper, raw-meal-free zone of the combustion chamber in relation to a height of the lower zone having a ratio of 5:1 to 1:1, and a third tertiary partial airstream line and a second raw meal partial stream passing into the rotary kiln exhaust gas rising line above a junction of a combustion chamber connecting line and the rotary kiln exhaust gas rising line in the upper region of the combustion chamber, and wherein each of the three tertiary partial airstream lines is assigned an actuating element for regulating a respective tertiary air flow rate, the method comprising:

• during a continuous operation of the cement clinker production line the actuating element which is arranged in the second tertiary partial airstream line connected to the junction region of the upper reducing zone and the lower zone of the combustion chamber is closed, whereas the actuating element which is arranged in the first tertiary partial airstream line connected to the upper side of the combustion chamber and the actuating element which is arranged in the third tertiary partial airstream line which leads into the rotary kiln exhaust gas rising line are open.