Low NOx calciner

A system for reducing NOx emission levels during the manufacture of cement clinker comprising a calciner unit further comprising:

• an upper portion;
• a lower portion;
• a NOx reduction zone in the lower portion having a refractory layer on the inside surface thereof;
• a tertiary air inlet in the upper portion for introducing tertiary air into the upper portion;
• a main calciner meal inlet located above the NOx reduction zone for introducing a main calciner meal portion into the upper portion;
• a first cooling calciner meal inlet located in the NOx reduction zone for introducing a first cooling calciner meal portion into a periphery of the NOx reduction zone for forming a peripheral layer of meal in the NOx reduction zone for protecting the refractory layer from hot kiln gas;
• a second cooling calciner meal inlet located in the NOx reduction zone;
• a fuel inlet located in or below the NOx reduction zone for introducing fuel into the NOx reduction zone for supporting a hot core of the hot kiln gas within the peripheral layer of the meal in the NOx reduction zone;
• wherein the first or second cooling calciner meal inlets located in the NOx reduction zone are arranged such that the cooling calciner meal portion is introduced tangentially into the NOx reduction zone;
• and
• a constriction located between the upper portion and lower portion for inhibiting the main calciner meal portion in the upper portion from entering the NOx reduction zone.